At non-towered airports, instead of receiving instructions from an
air traffic controller,
aircraft pilots 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 transmissions over a common frequency. For example, a
common traffic advisory frequency (CTAF) is recommended for radio communication and is used in the United States, Canada, New Zealand and Australia. Non-towered airports may lie inside or underneath controlled
airspace. 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; 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.
MTAF Some countries, such as Canada and Norway, 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.
UNICOM Many non-towered airports have radio to ground operations such as
UNICOM to assist aircraft arriving, departing, or maneuvering on the ground. These radio operators such as from
fixed-base operators 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 operations carrying out
aerial firefighting. For special events such as
fly-ins, 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 ==