What is Airport?

AirPort
The AirPort logo as seen in the Airport Utility icon.
Type:	Wireless Base Stations and Cards
Developer:	Apple Inc
Released:	July 21, 1999
Website:	Apple.com - AirPort Extreme Apple.com/jp - AirMac

AirPort is a local area wireless networking brand from Apple Inc. based on the IEEE 802.11b standard (also known as Wi-Fi) and certified as compatible with other 802.11b devices. A later family of products based on the IEEE 802.11g specification is known as AirPort Extreme. The latest family of products is based on the draft-IEEE 802.11n specification and carries the same name.

AirPort and AirPort Extreme in common usage can refer to the protocol (802.11b and 802.11g, respectively), the expansion card or the base station.

In Japan, the name "AirPort" had already been registered by I-O DATA, causing Apple to sell it under the name "AirMac" there.

Overview

AirPort debuted on July 21, 1999 at the Macworld Expo in New York City with Steve Jobs picking up an iBook supposedly to give the cameraman a better shot as he surfed the Web—the applause quickly built as people realized there were no wires. The initial offering included an optional expansion card for Apple's new line of iBook notebooks, plus an AirPort Base Station. The AirPort card (a repackaged Proxim—ORiNOCO Gold Card PC Card adapter) was later added as an option for almost all of Apple's product line, including PowerBooks, eMacs, iMacs, and Power Macs. Only Xserves do not have it as a standard or optional feature. The original AirPort system allowed transfer rates up to 11 Mbit/s and was commonly used to share Internet access and files between multiple computers.

On January 7, 2003, Apple introduced AirPort Extreme, based on the 802.11g specification. AirPort Extreme allows theoretical peak data transfer rates of up to 54 Mbit/s, and is fully backward-compatible with existing 802.11b wireless network cards and base stations. Several of Apple's current desktop computers and portable computers, including the MacBook Pro, MacBook, Mac mini, and iMac ship with an AirPort Extreme card as standard (as of May 2006). All other modern Macs have an expansion slot for the card. AirPort and AirPort Extreme cards are not physically compatible: AirPort Extreme cards cannot be installed in older Macs, and AirPort cards cannot be installed in newer Macs. The original AirPort card was discontinued in June 2004.

On June 7 2004, Apple released the AirPort Express Base Station as a lower-priced, more mass-market alternative to the AirPort Extreme Base Station.

On January 9 2007, Apple unveiled a new AirPort Extreme base station, now with styling similar to that of the Mac mini and Apple TV.^[1]

Although both AirPort and AirPort Extreme cards are available only for Macintosh computers, all AirPort base stations and cards are fully compatible with third-party base stations and wireless cards, so long as they conform to the 802.11a, 802.11b or 802.11g networking standards. Due to the nature of draft-n hardware, it is unlikely that the new model will interoperate with 802.11n routers from other manufacturers. However, due to the interoperability among previous models, it is not uncommon to see wireless networks composed of several types of AirPort base station serving both old and new Macintosh, Microsoft Windows, and even Linux systems. Apple's software drivers for AirPort Extreme also support some Broadcom and Atheros-based PCI Wireless adapters when fitted to PowerMac computers.

Base stations

An AirPort base station is used to connect AirPort-enabled computers to the Internet, each other, a wired LAN, and/or other devices.

AirPort

The original base station (known as Graphite) featured a modem and an Ethernet port. It was based on the same Lucent WaveLAN Bronze PC Card as the AirPort Card, and used an embedded 486 processor. It was released July 21, 1999. The Graphite AirPort Base Station is functionally identical to the Lucent RG-1000 wireless base station.

A second generation model (known as Dual Ethernet or Snow) was introduced on November 13 ,2001. It added a second Ethernet port, allowing it to share a wired network connection with both wired and wireless clients. Also new was the ability to connect to America Online's dial-up service—a feature unique to Apple base stations. This model was based on Motorola's PowerPC 860 processor.

AirPort Extreme (802.11g)

The AirPort Base Station was discontinued after the updated AirPort Extreme was announced on January 7, 2003. In addition to providing wireless connection speeds of up to a maximum of 54 Mbit/s, it adds an external antenna port and a USB port. The antenna port allows the addition of a signal-boosting antenna, and the USB port allows the sharing of a USB printer. A connected printer is made available via Bonjour's "zero configuration" technology and IPP to all wired and wireless clients on the network. A second model lacking the modem and external antenna port was briefly made available, but then discontinued after the launch of AirPort Express (see below). On April 19 2004, a third version, marketed as the 'AirPort Extreme Base Station (with Power over Ethernet and UL 2043), was introduced that supports Power over Ethernet and complies to the UL 2043 specifications for safe usage in air handling spaces, such as above suspended ceilings. All three models support the Wireless Distribution System (WDS) standard. The model introduced in January 2007 does not have a corresponding PoE, UL-compliant variant.

An AirPort Extreme base station can serve up to 50 wireless clients at once, and thus is more suitable for a corporate environment than the AirPort Express.

AirPort Express (802.11g)

The AirPort Express is a simplified and compact AirPort Extreme base station allowing only up to 10 networked users with a new feature called AirTunes. It did not replace the AirPort Extreme base station. It was introduced by Apple on June 7 2004 and includes an analog/optical audio mini-jack output, a USB port for remote printing, and a single Ethernet port.

The main processor in the AirPort Express is a Broadcom BCM4712KFB wireless networking chipset. This has a 200 MHz MIPS processor built in. The audio is handled by a Texas Instruments PCM2705 16-bit digital-to-analog converter.

The device can be used as an Ethernet-to-wireless bridge.

AirTunes

AirTunes allows an AirPort-enabled computer with the iTunes music player to simultaneously send a single stream of music to multiple (three to six, in typical conditions) stereos connected to an AirPort Express. The AirPort Express can be used to extend the range of existing AirPort Extreme networks by using WDS-bridging,^[2] which allows AirTunes functionality (as well as Internet access, file and printer sharing, etc.) to be extended across a larger distance and multiple wired and wireless clients.

Another use of the USB port is to control AirTunes using a Keyspan USB-enabled infrared remote control.

The AirPort Express's streaming media capabilities use the Apple's Remote Audio Output Protocol (RAOP), a proprietary variant of RTSP/RTP. Currently, the AirTunes system is not compatible with the Apple Remote's volume buttons. Likewise, AirTunes will not stream a video's audio. Several third-party AirPort Express clients exist to provide connectivity to an AirPort Express from sources other than iTunes, including Airfoil for Mac OS X and Windows, JustePort for Windows, and raop-play for Linux.

AirPort Extreme (802.11n)

The AirPort Extreme was updated on January 9 2007, to support the 802.11a/b/g and draft-n protocols. This revision also adds two LAN ports for a total of three.^[3] It now more closely resembles the 6.5-inch-square-shaped Apple TV and Mac Mini, and is about half the height of the Mini.

The new AirPort Disk feature allows users to plug a USB hard drive into the AirPort Extreme for use as a Mac OS X or Windows file server.^[4] Users may also connect a USB hub and printer, but they can not connect an external antenna.

On August 7, 2007, the AirPort Extreme was updated with Gigabit Ethernet to comply with most other Apple products.

As of September 24, 2007, there are a huge number of reports on the Apple Support Forum about problems with the USB port and printer/USB drive access (Internet remains fine). The problem started in mid-August with the firmware 7.2 and above. Apple has still to acknowledge the issue and release a fix.

• Symptoms:
• User cannot print (computer looks for printer but never to be found). The printer does not show in the AirPort Utility
• Cannot connect to USB drive. The Drive is visible in AirPort Disk Menu and in the AirPort Utility but trying to connect gives an error "password or user incorrect".

Turn on/off, disconnect/reconnect the drive and/or printer does not solve the issue. The only way to print and access the drive is to restart the AirPort Extreme. Some people using the first-generation AirPort Extreme (no Gigabit) have reported success to solve the issue by reverting to firmware earlier than 7.2 (which is impossible for the Gigabit model that can only use firmware 7.2 and later).

Several users also have noticed that the issue seems to only be occurring with Mac computers and not Windows machines, if the option to join the Windows workgroup is checked.

There is also a problem with NAT-PMP (Apple's equivalent to uPNP) with the latest 7.2.1 firmware, port forwarding is totally broken using NAT-PMP. A workaround is to downgrade to an earlier firmware, but this is not possible for the latest Gigabit ethernet-versions.

AirPort Cards

An AirPort Card is an Apple-branded wireless card used to connect to wireless networks such as those provided by an AirPort Base Station.

AirPort 802.11b Card

The original model, known as simply AirPort Card was a re-branded Lucent WaveLAN Gold PC card, in a modified housing that lacked the integrated antenna. It was designed to be capable of being user-installable. It was also modified in such a way that it could not be used in a regular PCMCIA slot (At the time it was significantly cheaper than the official WaveLAN Gold card).

AirPort Extreme 802.11g cards

Corresponding with the release of the AirPort Extreme Base Station, the AirPort Extreme Card became available as an option on the current models. It is based on a Broadcom 802.11g chipset and is housed in a custom enclosure that is mechanically proprietary, but is electrically compatible with the Mini PCI standard. It was also capable of being user-installed.

A different 802.11g card was included in the last iteration of the PowerPC-based PowerBooks and iBooks. A major distinction for this card was that it was the first "combo" card that included both 802.11g as well as Bluetooth. It was also the first card that was not user-installable. It was again a custom form factor, but was still electrically a Mini PCI interface for the Broadcom WLAN chip. A separate USB connection was used for the on-board Bluetooth chip.

Integrated AirPort Extreme 802.11a/b/g and /n cards

As AirPort Extreme began to come standard on all notebook models, Apple phased out the user-installable designs in their notebooks, iMacs and Mac Minis by mid 2005, moving to an integrated design. Airport continued to be an option, either installed at purchase or later, on the Power Mac G5 and the Mac Pro.

With the introduction of the Intel-based MacBook Pro in January 2006, Apple began to use a standard PCI Express mini card. Cards with this form factor are now used in all AirPort-equipped Macintoshes.

In early 2007, Apple announced that most Intel Core 2 Duo-based Macs, which had been shipping since October 2006, already included AirPort Extreme cards compatible with the draft-802.11n specification. 802.11n capability was unlocked by an enabler included with the new draft-802.11n-capable AirPort Extreme Base Station, or by purchasing the enabler separately from the Apple Store online.^[5] This card was also a PCI Express mini design, but used three antenna connectors in the notebooks and iMacs, in order to use a 2x3 MIMO antenna configuration. The cards in the Mac Pro and Apple TV have 2 antenna connectors and support a 2x2 configuration.

NB: To see which protocols your Airport card supports, start up the Network Utility (Applications -> Utilities) and take a look at the Model. Click here for a screenshot ^[6]

Security

AirPort and AirPort Extreme support a variety of security technologies to prevent eavesdropping and unauthorized network access. Cryptography plays a major role since wireless networks are vulnerable to eavesdropping, unlike wired networks which can, in most cases, be physically secured.

The original family of AirPort base stations, like most other Wi-Fi products, used 40-bit or 128-bit Wired Equivalent Privacy (WEP). AirPort Extreme and Express base stations retain this option, but also allow and encourage the use of Wi-Fi Protected Access (WPA) and, as of July 14, 2005, WPA2.

Generally, WEP is considered "broken." Holes were being found as early as 2001, and in March 2005, FBI officials showed they could crack a WEP key in three minutes using freely available tools from the Internet.^[7]

In response to concerns about WEP insecurity, the WPA standard was published in June 2003 as an intermediate solution. A new standard that uses the Advanced Encryption Standard (AES), called WPA2 or IEEE 802.11i, was ratified on June 24, 2004.

AirPort Extreme cards, using the Broadcom chipset, have the Media Access Control layer in software. The driver is closed source.

See also

• Apple Inc.
• IEEE 802.11
• iTunes
• Wi-Fi
• Wireless access point
• Wireless LAN

Notes

External links

• AirPort Extreme at Apple.com
• AirPort Express at Apple.com
• AirPort Support at Apple.com
• AirPort Extreme (802.11n) Setup Guide (PDF)
• Designing AirPort Networks Using Airport Utility (PDF)
• AirPort Base Station disassembly and benchmarks at iFixit

•  • [ e] Apple hardware since 1998
Consumer computers	eMac iBook (G3: Clamshell, Dual USB; G4) iMac (G3: Tray, Slot; G4; G5; Intel Core: Duo, 2 Duo, SR) MacBook Mac mini
Professional computers	MacBook Pro Mac Pro PowerBook (G3: Wallstreet, Lombard, Pismo; G4: Titanium, Aluminum) Power Mac (G3, Server, B&W; G4, Server, Cube; G5) Xserve (G4, CN; G5, CN; Intel)
Computing accessories	AirPort (Card, Express, Extreme) Cinema Display iSight Keyboard (Pro, Wireless) Mouse (Pro, Wireless, Mighty Mouse) USB Modem Xserve RAID
Consumer electronics	Apple TV iPhone iPod (classic: 1G, 2G, 3G, 4G, photo, 5G, 6G; mini: 1G, 2G; shuffle: 1G, 2G; nano: 1G, 2G, 3G; touch)
General accessories	Apple Remote iPod accessories (iPod Camera Connector, iPod Hi-Fi, Nike+iPod)
Italics indicate discontinued products.

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An airport is a facility where aircraft such as airplanes and helicopters operate. An airport minimally consists of one runway or helipad (for helicopters), for take offs and landings, and usually buildings as hangars, terminal buildings and a control center.

Additionally, an airport may have a variety of facilities and infrastructure, including fixed base operator services, air traffic control, passenger facilities such as restaurants and lounges, and emergency services. A military airport is known as an airbase or air station. The terms airfield, airstrip, and aerodrome may also be used to refer to airports of varying sizes. In some jurisdictions, the term airport is used where the facility is licensed as such by the relevant government organization (e.g. FAA, Transport Canada). Elsewhere the distinction is merely one of general appearance. Yet other areas define an airport by its having the necessary customs offices etc expected of a port.

Attributes

Airports vary in size, with smaller or less-developed airports often having only a single runway shorter than 1,000 m (3,300 ft). Larger airports for international flights generally have paved runways 2,000 m (6,600 ft) or longer. Many small airports have dirt, grass, or gravel runways, rather than asphalt or concrete.

In the United States, the minimum dimensions for dry, hard landing fields are defined by the FAR Landing And Takeoff Field Lengths. These include considerations for safety margins during landing and takeoff. Typically, heavier aircraft require longer runways. The longest public-use runway in the world is at Qamdo Bangda Airport, in Bangda, Qamdo, China. It has a length of 5,500 m (18,045 ft). The world's widest paved runway is at Ulyanovsk Vostochny Airport and is 105 m (344 ft) wide. As of 2006, there were approximately 49,000 airports around the world, including 14,858 in the United States alone.[https://www.cia.gov/library/publications/the-world-factbook/fields/2053.html]

Airport ownership and operation

Most of the world's airports are owned by local, regional, or national government bodies who then lease the airport to private corporations who oversee the airport's entire operation. For example, the British firm BAA plc operates seven of the commercial airports in the United Kingdom, as well as several other airports outside of the UK. Germany's Frankfurt International Airport is managed by the quasi-private firm Fraport AG.

In the United States, most airports are operated directly by government entities or government-created airport authorities (also known as port authorities). Only Indianapolis International Airport, which is owned by the City of Indianapolis and leased to BAA Indianapolis, Inc., a subsidiary of the British airport firm BAA plc, and Stewart International Airport in New York's Hudson Valley, are entirely operated by a private entity. Stewart International Airport was the nation's first privatized commercial airport and operates under a 99-year lease agreement with the New York State Department of Transportation. National Express Group, Inc., operates Stewart International Airport and is the United States subsidiary of the National Express Group, plc, in the United Kingdom.



Many U.S. airports still lease part or all of their facilities to outside firms, who operate specific functions such as retail management and parking. In the United States, all commercial airport runways are certified by the Federal Aviation Administration, but maintained by the local airport under the regulatory authority of the FAA.

Despite the reluctance to privatize airports in the United States (despite the FAA sponsoring a privatization program since 1996), the government-owned, contractor-operated (GOCO) arrangement is the standard for the operation of commercial airports in the rest of the world.

In New Zealand, Auckland International Airport, the nation's main international airport, is fully privatised. Ownership and operation of the 1,497 hectare complex is vested entirely with Auckland International Airport Limited, a public company, with the only governmental involvement being Airways Corporation of New Zealand's operation of air traffic control systems. Similar arrangements pertain to Wellington and Christchurch airports, and most other main airports are operated by private companies.

In Argentina, 32 airports including the main airport Ezeiza International Airport are operated by Aeropuertos Argentina 2000, a private company. On the other hand, 3 airports are operated by another company named London Supply.

Airport structures

Airports are divided into landside and airside areas. Landside areas include parking lots, public transportation stations, tank farms and access roads. Airside areas include all areas accessible to aircraft, including runways, taxiways and ramps. Access from landside areas to airside areas is tightly controlled at most airports. Passengers on commercial flights access airside areas through terminals, where they can purchase tickets, clear security, check or claim luggage and board aircraft through gates. The waiting areas which provide passenger access to aircraft are typically called concourses, although this term is often used interchangeably with terminal.

The area where aircraft park next to a terminal to load passengers and baggage is known as a ramp (or, to the media and uninitiated, "the tarmac"). Parking areas for aircraft away from terminals are generally called aprons

Both large and small airports can be towered or non-towered, depending on air traffic density and available funds. Due to their high capacity and busy airspace, most international airports have air traffic control located on site.

Airports with international flights have customs and immigration facilities. However, as some countries have agreements that allow travel between them without customs and immigrations, such facilities are not a definitive need for an international airport. International flights often require a more conspicuous level of physical security, although in recent years, many countries have adopted the same level of security for international and domestic travel.

Modern engineers and architects are developing "floating airports" which could be located several miles at sea and which would utilize designs such as Float Incorporated's Pneumatic Stabilized Platform (PSP) technology.

Shops and food services

Airports have a captive audience, and consequently the prices charged for food are generally higher than are available elsewhere in the region. However, some airports, such as JFK's Terminal 8, guarantee prices comparable to those outside of the airport. Airport fees are fees commonly paid for use of services of airports, such as in the Subic Bay International Airport, known for charging airport fees. However, some airports now regulate food costs to keep them comparable to so-called "street prices". This term is a bit misleading as prices often match the MSRP but are almost never discounted.

Premium and VIP Services

Several mid-large size airports also have facilities for premium passengers. In the United States, these lounges are typically for international or long-haul first and business class passengers, paid members, and elite-level frequent fliers on long haul flights (regardless of what class they are in). In the rest of the world, the lounges are not open to purchase, but can be used by all premium passengers and most elite frequent fliers. Some lounges are comparatively spartan and only offer a quiet place to sit and work; other lounges include meals and massage services.

Cargo and freight services

In addition to people, airports are responsible for moving large volumes of cargo around the clock. Cargo airlines often have their own on-site and adjacent infrastructure to rapidly transfer parcels between ground and air modes of transportation.

Support services

Aircraft maintenance, pilot services, aircraft rental, and hangar rental are most often performed by a fixed base operator (FBO). At major airports, particularly those used as hubs, airlines may operate their own support facilities.

Some airports, typically military airbases, have long runways used as emergency landing sites. Many airbases have arresting equipment for fast aircraft, known as Rotary Hydraulic Arrester Gear - a strong cable suspended just above the runway and attached to a hydraulic reduction gear mechanism. Together with the landing aircraft's arresting hook, it is used in situations where the brakes would have little or no effect.

Airport access

Many large airports in the world are located next to or even above railway trunk routes, for instance Frankfurt International Airport, Amsterdam-Schiphol Airport, London Heathrow Airport, London Gatwick Airport and London Stansted. For local access, many airports have local train lines, rapid transit, light rail lines or other mass transit systems, for instance the AirTrain JFK at John F. Kennedy International Airport in New York and the Silver Line T at Boston's Logan International Airport by the MBTA (Massachusetts Bay Transportation Authority). These systems are usually directly connected to the main terminals. Large airports usually have access also through freeways from which cars fed into two access roads, designed as loops, one sitting on top of the other. One level is for departing passengers and the other is for arrivals. This road concept was pioneered at Los Angeles International Airport.

History and development

The earliest airplane takeoff and landing sites were simply open, grassy fields. The plane could approach at any angle that provided a favorable wind direction. A slight improvement was the dirt-only field, which eliminated the drag from grass. However, these only functioned well in dry conditions. They would eventually be replaced by concrete surfaces that allowed all-weather landings in both daylight and at night.

Early airfields were often built for the purpose of entertainment. These aerodromes consisted of a grassy field, with a hangar for storage and servicing of airplanes, and observation stands for visitors.



The title of "world's oldest airport" is disputed, but College Park Airport in Maryland, USA, established in 1909 by Wilbur Wright, is generally agreed to be the world's oldest continually operating airfield^[8], although it presently serves only general aviation traffic. Amsterdam Schiphol Airport opened on September 16, 1916 as a military airfield, but only accepted civil aircraft from December 17, 1920, allowing Kingsford Smith International Airport in Sydney, Australia — which started operations in January 1920 — to claim to be the world's oldest continually operating commercial airport.^[9].

The first known usage of the term "airport" appeared in a newspaper article in 1919, in reference to Bader Field in Atlantic City, New Jersey.^[10]

Increased aircraft traffic during World War I led to the construction of regular landing fields. Airplanes had to approach these from certain directions. This led to the development of aids for directing the approach and landing slope.

Following the war, some of these military airfields added commercial facilities for handling passenger traffic. One of the earliest such fields was Le Bourget, near Paris. The first international airport to open was the Croydon Airport, in South London [4]. In 1922, the first permanent airport and commercial terminal solely for commercial aviation was built at Königsberg, Germany. The airports of this era used a paved "apron", which permitted night flying as well as landing heavier airplanes.

The first lighting used on an airport was during the later part of the 1920s; in the 1930s approach lighting came into use. These indicated the proper direction and angle of descent. The colors and flash intervals of these lights became standardized under the ICAO. In the 1940s, the slope-line approach system was introduced. This consisted of two rows of lights that formed a funnel indicating an aircraft's position on the glideslope. Additional lights indicated incorrect altitude and direction.

Following World War II, airport design began to become more sophisticated. Passenger buildings were being grouped together in an island, with runways arranged in groups about the terminal. This arrangement permitted expansion of the facilities. But it also meant that passengers had to travel further to reach their plane.

An improvement in the landing field was the introduction of grooves in the concrete surface. These ran perpendicular to the direction of the landing aircraft and served to draw off excess water in rainy conditions that could build up in front of the plane's wheels.

Airport construction boomed during the 1960s with the increase in jet aircraft traffic. Runways were extended out to 3 km (9800 ft). The fields were constructed out of reinforced concrete using a slip-form machine that produces a continual slab with no disruptions along the length.

Modern landing fields are thickest in the area where the plane touches down in order to support the force of the landing gear touching down. Runways are constructed as smooth and level as possible using measuring devices to correct for variations in height.

Airport designation and naming

Main article: List of airports

Airports are uniquely represented by their IATA airport code and ICAO airport code. IATA airport codes are often abbreviated forms of the common name of the airport, such as PHL for Philadelphia International Airport. Airports sometimes retain their previous IATA code when an airport's name is changed. O'Hare International Airport in Chicago retains the IATA code ORD, from its former name of Orchard Field.

The name of the airport itself can be its location, such as Los Angeles International Airport. It can be the name of a prominent national celebrity, commonly a politician, e.g. John F. Kennedy International Airport, Ninoy Aquino International Airport, Indira Gandhi International Airport, Atatürk Airport, Lester B. Pearson International Airport or Charles de Gaulle International Airport. Airports may also be named after a person associated with the region it serves or prominent figures in aviation history, such as Will Rogers World Airport, Liverpool John Lennon Airport, Kingsford Smith International Airport, or more recently Belfast City Airport was renamed George Best Belfast City Airport in memory of the football star who was born in Northern Ireland.

Airport security

Main article: Airport security

Baggage is scanned using X-ray machines, passengers walk through metal detectors

Airports are required to have safety precautions in most countries. Rules vary in different countries, but there are common elements worldwide. Airport security normally requires baggage checks, metal screenings of individual persons, and rules against any object that could be used as a weapon. Since the September 11, 2001 attacks, airport security has been dramatically increased worldwide.

Airport operations

Outside the terminal, there is a large team of people who work in concert to ensure aircraft can land, take off, and move around quickly and safely. These processes are largely invisible to passengers, but they can be extraordinarily complex at large airports.

Air traffic control

The vast majority of the world's airports are non-towered, with no air traffic control presence at all. However, at particularly busy airports, or airports with other special requirements, there is an air traffic control (ATC) system whereby controllers (usually ground-based) direct aircraft movements via radio or other communications links. This coordinated oversight facilitates safety and speed in complex operations where traffic moves in all three dimensions. Air traffic control responsibilities at airports are usually divided into at least two main areas: ground and tower, though a single controller may work both stations. The busiest airports also have clearance delivery, apron control, and other specialized ATC stations.

Ground Control is responsible for directing all ground traffic in designated "movement areas," except the traffic on runways. This includes planes, baggage trains, snowplows, grass cutters, fuel trucks, and a wide array of other vehicles. Ground Control will instruct these vehicles on which taxiways to use, which runway they will use (in the case of planes), where they will park, and when it is safe to cross runways. When a plane is ready to take off it will stop short of the runway, at which point it will be turned over to Tower Control. After a plane has landed, it will depart the runway and be returned to Ground Control.



Tower Control controls aircraft on the runway and in the controlled airspace immediately surrounding the airport. Tower controllers may use radar to identify and accurately locate an aircraft's position in three-dimensional space, or they may rely on pilot position reports and visual observation. They coordinate the sequencing of aircraft in the traffic pattern and direct aircraft on how to safely join and leave the circuit. Aircraft which are only passing through the airspace must also contact Tower Control in order to be sure that they remain clear of other traffic and do not disrupt operations.

Traffic pattern

All airports use a traffic pattern (often called a traffic circuit outside the U.S.) to assure smooth traffic flow between departing and arriving aircraft. Generally, this pattern is a circuit consisting of five "legs" that form a rectangle (two legs and the runway form one side, with the remaining legs forming three more sides). Each leg is named (see diagram), and ATC directs pilots on how to join and leave the circuit. Traffic patterns are flown at one specific altitude, usually 800 or 1000 ft. above ground level (AGL). Standard traffic patterns are left-handed, meaning all turns are made to the left. Right-handed patterns do exist, usually because of obstacles such as a mountain, or to reduce noise for local residents. The predetermined circuit helps traffic flow smoothly because all pilots know what to expect, and helps reduce the chance of a mid-air collision.

At extremely large airports, a circuit is in place but not usually used. Rather, aircraft (usually only commercial with long routes) request approach clearance while they are still hours away from the airport, often before they even take off from their departure point. Large airports have a frequency called Clearance Delivery which is used by departing aircraft specifically for this purpose. This then allows airplanes to take the most direct approach path to the runway and land without worrying about interference from other aircraft. While this system keeps the airspace free and is simpler for pilots, it requires detailed knowledge of how aircraft are planning to use the airport ahead of time and is therefore only possible with large commercial airliners on pre-scheduled flights. The system has recently become so advanced that controllers can predict whether an aircraft will be delayed on landing before it even takes off; that aircraft can then be delayed on the ground, rather than wasting expensive fuel waiting in the air.

Navigational aids

When flying, there are a number of aids available to pilots, though not all airports are equipped with them. A Visual Approach Slope Indicator (VASI) helps pilots fly a perfect approach for landing once they have found the airport. Some airports are equipped with a VHF omnidirectional range (VOR) to help pilots find the direction to the airport. VORs are often accompanied by a Distance Measuring Equipment (DME) to determine the distance to the VOR. VORs are also located off airports, where they serve to provide airways for aircraft to navigate upon. In poor weather, pilots will use an Instrument Landing System to find the runway and fly the correct approach, even if they cannot see the ground. The number of instrument approaches based on the use of the Global Positioning System (GPS) is rapidly increasing and may eventually be the primary means for instrument landings.

Larger airports sometimes offer Precision Approach Radar (PAR), but these systems are more common at military air bases than civilian airports. The aircraft's horizontal and vertical movement is tracked via radar, and the controller tells the pilot his position relative to the approach slope. Once the pilots can see the runway lights, they may continue with a visual landing.

Guidance signs

Airport guidance signs provide direction and information to taxiing aircraft and airport vehicles and assist in safe and expedient movement of aircraft. Smaller airports may have few or no signs, relying instead on airport diagrams and charts.

There are two classes of signage at airports, with several types of each:

Operational guidance signs

• Location signs - yellow on black background. Identifies the runway or taxiway currently on or entering.
• Direction/Runway Exit signs - black on yellow. Identifies the intersecting taxiways the aircraft is approaching, with an arrow indicating the direction to turn.
• Other - Many airports use conventional traffic signs such as stop and yield signs throughout the airport.

Mandatory instruction signs

Mandatory instruction signs are white on red. They show entrances to runways or critical areas. Vehicles and aircraft are required to stop at these signs until the control tower gives clearance to proceed.

• Runway signs - White on a red. These signs simply identify a runway intersection ahead.
• Frequency Change signs - Usually a stop sign and an instruction to change to another frequency. These signs are used at airports with different areas of ground control.
• Holding Position signs - A single solid yellow bar across a taxiway indicates a position where ground control may require a stop. If two solid yellow bars and two dashed yellow bars are encountered, this indicates a holding position for a runway intersection ahead; runway holding lines must never be crossed without permission. At some airports, a line of red lights across a taxiway is used during low visibility operations to indicate holding positions.

Lighting

Many airports have lighting that help guide planes using the runways and taxiways at night or in rain or fog.

On runways, green lights indicate the beginning of the runway for landing, while red lights indicate the end of the runway. Runway edge lighting consists of white lights spaced out on both sides of the runway, indicating the edge. Some airports have more complicated lighting on the runways including lights that run down the centerline of the runway and lights that help indicate the approach (an Approach Lighting System, or ALS). Low-traffic airports may use Pilot Controlled Lighting to save electricity and staffing costs.

Along taxiways, blue lights indicate the taxiway's edge, and some airports have embedded green lights that indicate the centerline.

Wind indicators

Planes take-off and land into the wind in order to achieve maximum performance. Wind speed and direction information is available through the ATIS or ATC, but pilots need instantaneous information during landing. For this purpose, a windsock is kept in view of the runway.

Safety management

Air safety is an important concern in the operation of an airport, and almost every airfield includes equipment and procedures for handling emergency situations. Commercial airfields include one or more emergency vehicles and their crew that are specially equipped for dealing with airfield accidents, crew and passenger extractions, and the hazards of highly flammable airplane fuel. The crews are also trained to deal with situations such as bomb threats, hijacking, and terrorist activities.

Potential airfield hazards to aircraft include debris, nesting birds, and environmental conditions such as ice or snow. The fields must be kept clear of debris using cleaning equipment so that loose material doesn't become a projectile and enter an engine duct. In adverse weather conditions, ice and snow clearing equipment can be used to improve traction on the landing strip. For waiting aircraft, equipment is used to spray special deicing fluids on the wings.



Many airports are built near open fields or wetlands. These tend to attract bird populations, which can pose a hazard to aircraft in the form of bird strikes. Airport crews often need to discourage birds from taking up residence.

Some airports are located next to parks, golf courses, or other low-density uses of land. Other airports are located near densely-populated urban or suburban areas. In the 1980's, a conflict arose in San José, California, when a plane attempting to land at Reid-Hillview Airport (built in the 1930's) collided with a Macy's department Store at the Eastridge shopping mall. Many local residents tried to get the airport shut down, even though it had been there for fifty years: their neighborhoods (and the mall) were about a decade old.

Depending on their configuration, an airport can have sections of their pavement where collisions between airplanes on the ground can tend to occur. Records are kept of any incursions where airplanes or vehicles are in an inappropriate location, allowing these "hot spots" to be identified. These locations then undergo special attention by transportation authorities (such as the FAA in the US) and airport administrators in order to reduce accidents.

During the 1980s, a phenomenon known as microburst became a growing concern due to accidents caused by microburst wind shear. (For example, see Delta Air Lines Flight 191.) Microburst radar was developed as an aid to safety during landing, giving two to five minutes warning to aircraft in the vicinity of the field of a microburst event.

Some airfields now have a special surface known as soft concrete at the end of the runway that behaves somewhat like styrofoam, bringing the plane to a relatively rapid halt as the material disintegrates. These surfaces are useful when the runway is located next to a body of water or other hazard, and prevent the planes from overrunning the end of the field.

Airport ground crew

Main article: Ground Support Equipment

Most airports have ground crew handling the loading and unloading of passengers, crew, baggage and other services.

Some ground crew are linked to specific airlines operating at the airport.

Environmental concerns

The traffic generated by airports both in the air and on the surface can be a major source of aviation noise and air pollution which may interrupt nearby residents' sleep and produce other noise health effects. The construction of new airports, or addition of runways to existing airports, is often resisted by local residents because of the effect on the countryside, historical sites, local flora and fauna. As well, due to the risk of collision between birds and airplanes, large airports undertake population control programs where they frighten or shoot birds to ensure the safety of air travellers.

The construction of airports has been known to change local weather patterns. For example, because they often flatten out large areas, they can be susceptible to fog in areas where fog rarely forms. In addition, because they generally replace trees and grass with pavement, they often change drainage patterns in agricultural areas, leading to more flooding, run-off and erosion in the surrounding land.

Military airbase

Main article: Airbase

An airbase, sometimes referred to as a military airport or airfield, provides basing and support of military aircraft. Some airbases provide facilities similar to their civilian counterparts. For example, RAF Brize Norton in Oxfordshire, England has a terminal which caters to passengers for the Royal Air Force's scheduled Tristar flights to the Falkland Islands. Military airbases may also be co-located with civilian airports, sharing the same tower/air traffic control facilities, runways, taxiways and emergency services, but with separate terminals, parking areas, hangars and shelter areas. Examples of this are Bardufoss Airport/Bardufoss Air Station and Gardermoen Airport/Gardermoen Air Station, both in Norway. A special variant of a military airfield is the Aircraft Carrier.

Aircraft carriers

Main article: Aircraft carrier

An aircraft carrier is a warship that functions as a floating airport for military aircraft. Aircraft carriers allow a naval force to project air power great distances without having to depend on local bases for land-based aircraft. After their development in World War I, aircraft carriers replaced the battleship as the centrepiece of a modern fleet during World War II. Unescorted carriers are considered vulnerable to missile or submarine attacks and therefore travel as part of a carrier battle group that includes a wide array of other ships with specific functions.

Airports in entertainment

Airports have occasionally played major roles in motion pictures and television shows due to being transportation hubs, but also because of their unique characteristics. One such example of this is the movie The Terminal, a film about a man who becomes permanently grounded in an airport terminal and must survive only on the food and shelter provided by the airport. Movies such as Airplane!, Airport, , Jackie Brown, Get Shorty, Unaccompanied Minors, Catch Me If You Can and The Langoliers, as well as television series like Lost also have significant parts of their story set within airports.

Also, several computer simulation games were created in which the player is in charge of an airport. Names include Airport Tycoon and the sequels; Airport Tycoon 2 and Airport Tycoon 3. There is also a Japanese series of games called Air Traffic Controller.

Airport directories

Each national aviation authority has a source of information about airports in their country. This would usually contain information such as elevation, airport lighting, runway information, communications, hours of operation, nearby NAVAIDs and much more.

• The United States uses the Airport/Facility Directory (A/FD), published in seven volumes.
• In Canada, a single publication, the Canada Flight Supplement (CFS) provides equivalent information.
• In the United Kingdom and the Republic of Ireland, the equivalent information is found in Pooley's Flight Guide, a publication compiled with the assistance of the Civil Aviation Authority (CAA). Pooley's also contains information on some continental European airports that are close to Great Britain.
• The most comprehensive, consumer/business directory of commercial airports in the world (primarily for airports as businesses, rather than for pilots) is organized by the trade group Airports Council International.

References

See also

• Airport ramp
• Airport terminal
• Domestic airport
• Ground Support Equipment
• Heliport
• International airport
• List of airports
• List of aviation topics
• List of hub airports
• Megaproject
• Model airport
• NIMBY
• Pneumatic Stabilized Platform (PSP) (floating airport)
• Port
• Regional airport
• STOLport
• Total Airport Management Systems
• World's busiest airport

External links

• AirNav.com - complete list of U.S. airports, with detailed airport information
• fboweb.com - graphical airport finder via Google Maps
• ATCSCC Real-time Airport Status page - shows airport delay times for major U.S. airports (FAA)
• Department for Transport (United Kingdom)
• History of Aircraft Landing Aids
• Airport satellite images
• SkyVector.com - Airspace and Airport information on Aeronautical Charts
• Canadian Air Transport Security Authority (CATSA) Official Website
• View airports and weather in Google Maps and Google Earth
• Float Incorporated (developers of floating airports and Pneumatic Stabilized Platform (PSP))