aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes airplane, fixed-wing and helicopter, rotary-wing types, morphable wings, wing-less lifting bodies, as well as aerostat, lighter- ...

, a non-towered airport is an

airport An airport is an aerodrome with extended facilities, mostly for commercial air transport. Airports usually consists of a landing area, which comprises an aerially accessible open space including at least one operationally active surfa ...

without a

control tower Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled air ...

, or

air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airsp ...

(ATC) unit. The vast majority of the world's airports are non-towered. In the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

, there are close to 20,000 non-towered airports compared to approximately 500 airports with control towers. Airports with a control tower without

24/7 In commerce and industry, 24/7 or 24-7 service (usually pronounced "twenty-four seven") is service that is available at any time and usually, every day. An alternate orthography for the numerical part includes 24×7 (usually pronounced "twenty ...

ATC service follow non-towered airport procedures when the tower is closed but the airport remains open, for example at night.

Operations

At non-towered airports, instead of receiving instructions from an

air traffic controller Air traffic control specialists, abbreviated ATCS, are personnel responsible for the safe, orderly, and expeditious flow of air traffic in the global air traffic control system. Usually stationed in air traffic control centers and control ...

aircraft pilot An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators, because they a ...

s follow recommended operations and communications procedures for operating at an airport without a control tower. The exact procedures vary from country to country, but they may include standard arrival and departure procedures, as well as a common communications phraseology by

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a tr ...

transmissions over a common frequency. For example, a

common traffic advisory frequency Common traffic advisory frequency (CTAF) is the name given to the VHF radio frequency used for air-to-air communication at United States, Canadian and Australian non-towered airports. Many towered airports close their towers overnight, keeping ...

(CTAF) is recommended for radio communication and is used in the

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

and

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

. Non-towered airports may lie inside or underneath controlled

airspace Airspace is the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere. It is not the same as aerospace, which is th ...

. In that case, some or all aircraft arriving and departing require clearances from a remote air traffic control unit, such as terminal or center control, even though there is no control tower managing landings and takeoffs. Pilots may be able to obtain those clearances by radio, by phone, or through a company dispatcher or local

flight service station A flight service station (FSS) is an air traffic facility that provides information and services to aircraft pilots before, during, and after flights, but unlike air traffic control (ATC), is not responsible for giving instructions or clearances or ...

; in some cases, departing aircraft ( IFR or VFR) take off and level out below the floor of controlled airspace, then radio for a clearance before climbing further. Some countries establish low-altitude VFR corridors for non-towered airports in large urban areas so that VFR arrivals and departures can avoid controlled airspace altogether. Airport Traffic Pattern from AIM 4-3-2

MTAF

Some countries, such as Canada and

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of ...

, use mandatory frequency airports (MF) or mandatory traffic advisory airports (MTAF), which operate like towered airports in some ways: the radio operators (typically a flight service station) still issue only advisories, but aircraft are required to make radio contact with the ground station before operating in the airport's

control zone A control zone (CTR) in aviation is a volume of controlled airspace, usually situated below a control area, normally around an airport, which extends from the ''surface'' to a ''specified upper limit'', established to protect air traffic operating ...

UNICOM

Many non-towered airports have radio to ground operations such as

UNICOM A UNICOM (universal communications) station is an air-ground communication facility operated by a non-air traffic control private agency to provide advisory service at uncontrolled aerodromes and airports and to provide various non-flight services ...

to assist aircraft arriving, departing, or maneuvering on the ground. These radio operators such as from

fixed-base operator A fixed-base operator (FBO) is an organization granted the right by an airport to operate at the airport and provide aeronautical services such as fueling, hangaring, tie-down and parking, aircraft rental, aircraft maintenance, flight instructio ...

s have no authority to give aircraft clearances or instructions, but they can issue advisories to let them know about weather conditions, runway conditions, traffic, and other concerns.

Temporary towers

A mobile airport traffic control tower (MATCT) is a temporary tower in an area with an immediate increase in air traffic density. This may be due to

wildfire suppression Wildfire suppression is a range of firefighting tactics used to suppress wildfires. Firefighting efforts in wild land areas require different techniques, equipment, and training from the more familiar structure fire fighting found in populated ...

operations carrying out

aerial firefighting Aerial may refer to: Music * ''Aerial'' (album), by Kate Bush * ''Aerials'' (song), from the album ''Toxicity'' by System of a Down Bands * Aerial (Canadian band) * Aerial (Scottish band) *Aerial (Swedish band) Performance art *Aerial silk ...

. For special events such as

fly-in A fly-in is a pre-arranged gathering of aircraft, pilots and passengers for recreational and social purposes. Fly-ins may be formally or informally organised, members of the public may or may not be invited, the gathering may be at an airport ...

s, temporary towers may operate for only several days each year at fields that are otherwise non-towered. Temporary towers may operate out of an existing airport building, an RV, or even simply a chair (with a portable transmitter and binoculars).

Criteria

When the traffic volume at an airport gets too high for safe and efficient operations, or when the mix of aircraft types and speeds becomes too large, an airport may be considered for a tower. However, it is also necessary to find the money to construct a building and pay the controllers' salaries; in some cases aviation regulations or local opposition may prevent establishment of the unit.{{Cite web, url=https://www.aopa.org/advocacy/advocacy-briefs/air-traffic-services-process-brief-criteria-for-establishing-air-traffic-control-towers-and-the-contract-tower-program, title=Air Traffic Services Process Brief -- Criteria For Establishing Air Traffic Control Towers and the Contract Tower Program, date=2016-07-15, website=www.aopa.org, access-date=2018-06-08

Risk

Hazards are created by failure to use radios to report positions and intentions when operating within the airspace, which can lead to collisions between aircraft unaware of each other. In 1996, an incoming United Express Flight 5925 collided with a King Air aircraft, which failed to report its intent to take off on a common traffic advisory frequency at non-towered Quincy Airport in

Illinois Illinois ( ) is a state in the Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolitan areas include, Peoria and Rock ...

. Some pilots fail to use the correct runway at non-towered airports.

References

Airports by type