Bawt
With the recent flight switches taking place at LHR, BA have taken to changing the callsigns of their ex T1 short Haul flights now operating into T4, to BAWT (Speedbird Tango)
For example tonights BA399 would be BAWT399, and flightplans etc seem to confirm this is being used officialy.
How does this comply with previously held standards where a callsign would be displayed with only 3 letters?