When filing a flight plan, civil aircraft may use either their registration number or a three letter contraction followed by a flight number. In the RW, the total callsign cannot exceed seven characters; this limit is not enforced on vatsim, so you will often see callsigns of more than seven characters.
Callsign using registration number
U.S. registered civilian aircraft are all issued a registration number beginning with the letter "N."
Prefixes of “L” or “T” may be used prior to the "N" in the callsign. “L” indicates a Lifeguard flight; “T” indicates that it is an air taxi flight. As stated above, do not give priority to lifeguard flights on vatsim.
When the controller initiates communication with an aircraft, he should state the callsign, speaking each digit individually and using phonetic pronunciation for the letters (except when “L” is used as a prefix, see below for an example) . For example:
If a pilot calls and uses his aircraft type in his callsign, you may do the same. For example:
Authorized Callsigns
The FAA will authorize callsigns for certain companies. On vatsim, there is no oversight of these callsigns and pilots may use them at their discretion. When communicating with these aircraft, state the callsign followed by the flight number in group form. For example:
Zeros can be tricky in callsigns. If present they must be used in either group form or individual form, if needed. For example:
The following abbreviations are used for military flights:
On vatsim, pilots don't always follow official guidance on callsign construction. The most basic military callsign, is the service identifier (see above) followed by a serial number. State the service name followed by the number. For example:
Military pilots may also choose a pronounceable word as a callsign followed by a number (in the RW, this combination cannot exceed seven characters, this limit is not enforced on vatsim). For example:
Foreign registered aircraft often have registration numbers composed of only letters. In these cases phonetic pronunciation is optional. For example:
For foreign air carriers, you may use separte digits in the callsign in place of group form, if that is used by the pilot. For example:
{Reference: FAAO 7110.65 2-3-5 & 2-4-20}
Abbreviated callsigns
After communications have been established, you may abbreviate the callsign of aircraft that do not use an authorized callsign. For example:
Except for center controllers, heavy aircraft must always be identified by appending the term “heavy” to the end of the callsign. A pilot of a heavy aircraft should file “H/” prior to his aircraft type when filing a flight plan. The 7110.65 appendix A also identifies heavy aircraft. For example: