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A callsign is a unique nickname used primarily over wireless communications for brevity.

Callsigns assigned to pilots and flight officers can play on the aviator's name, or can be based on specific circumstances or attributes (sometimes comical). Examples:

Such callsigns are also used informally outside of wireless communication. For example, Karl Agathon is often in conversation referred to by his callsign "Helo" rather than his given name outside of the cockpit.

Specific military callsigns are reserved for certain positions or functions rather than any individuals. A ship's commander will assume the callsign "actual," e.g. "Galactica actual," "Pegasus actual," "Demetrius actual," etc. These callsigns are not for informal use.

Ships can also have callsigns. Viper and Raptor callsigns are based on tail numbers (Viper 7242, Raptor 718).

The callsign "Colonial One" is reserved for the vessel carrying or designated for the sitting Colonial President, similar to the way the United States Air Force and Marine Corps designate "Air Force One" and "Marine One" as the President's official air transport and helicopter respectively. "Colonial Heavy 798" assumes the callsign "Colonial One" after Laura Roslin is sworn in as President following confirmation of the deaths of President Adar during the Cylon attack on the Twelve Colonies.