Recently a few pictures and links have been going around featuring a couple very early examples of radio in aircraft.
This 1915 model looks very sharp:
Aircraft radio telephony transmitter, complete with round valve and microphone, made by CE Prince, 1915. This was the first successful air-to-ground radio telephony set, used at Brooklands in 1915 to transmit voice over wireless from an aircraft to the ground.
Another one like it, without the tube, is in a museum that has pictures online:
Rather heady-stuff when new!