An aircraft call sign can be abbreviated after satisfactory communication has been established, no confusion is likely to arise and...

Question

Accepted Answer

after the abbreviated call sign has been used by the ground station.

Answer

after the aircraft station and ground station agree to use the abbreviated call sign.

Answer

if there are a lot of other communications on the frequency.

Answer

if the aircraft station deems it necessary to call the ground station with its abbreviated call sign.

Crowdly