Aviation call signs

Call signs in aviation are derived from several different policies, depending upon the type of flight operation and whether or not the caller is in an aircraft or at a ground facility.

In this case, the call sign is spoken using the International Civil Aviation Organization (ICAO) phonetic alphabet.

[2] After an aircraft has made contact with an air traffic control facility, the call sign may be abbreviated.

[4] Air taxi operators in the United States sometimes do not have a registered call sign, in which case the prefix T is used, followed by the aircraft registration number (e.g., Tango-November-Niner-Seven-Eight-Charlie-Papa).

Some variations of call signs exist to express safety concerns to all operators and controllers monitoring the transmissions.

Although the Boeing 757's MTOW is less than 136 tons, it is categorized as a heavy aircraft because it generates strong wake turbulence.

[5] For air ambulance services or other flights involving the safety of life (such as aircraft carrying a person who has suffered a heart attack), "Medevac" is prefixed to the call sign.

[7] Australia's Royal Flying Doctors Service (RFDS) is using "FlyDoc" following by three numbers assigned to the aircraft as their call signs.

The intent of this call sign was to raise the air traffic control operators' awareness of the unique performance of the aircraft and the special attention it required.

Before these registrations came in (between 2004 and 2008), they used to use and normally still do use, either a three letter code issued to all gliders by the British Gliding Association known as the aircraft's Trigraph.

Some gliders are still not required to carry a CAA General Aviation type registration as they are older designs or prototypes and can therefore only continue to use their Trigraph or Competition number as a call sign.

Administrative call signs are used with air traffic control facilities similar to those of commercial operators.

For example, Royal Canadian Air Force 442 Rescue Squadron, based at Comox, British Columbia uses the call sign "Snake 90x" depending on the tail number of the helicopter: 901, 902, etc.

A general aviation aircraft in the United States with its FAA civilian registration number (N98710), which also doubles as its call sign, displayed on the fuselage. However, since this is a Civil Air Patrol aircraft, it will generally be identified by CAPxxxx, based on the state from which it hails.