Do you have trouble enunciating any particular callsigns?
One that I have heard a pilot stumble over was AYT.
He called up, "Sydney, this is Alfa Yankee Tangee..... errrr... Alfo Yanko Tango ... err ... Yalfo Anky ..... ahh, stuff it, Ay Why Tee!!"
Others get abbreviated out of existence - Polair One's original callsign was Papa Hotel Whisky, which Chucky would shorten to "Parteliski".
Another was Bravo Hotel Uniform, which in JB-speak was "Brartelform".
Got any others?
