[Testerchild]

One experiment with wireless telephony is recorded in 'The War in the Air' Volume 6, page 464, but not between aircraft:although I'm sure I have read of such experiments somewhere. The W/T experiment in WITA was from aircraft to tanks, of all things, in the run-up to the Battle of Amiens in 1918.

"Experiments were made with wireless telephony by which the air observers might communicate information, but it was found that talk from the air could be heard inside a tank only under the most favourable conditions and so long as the aeroplane was within a quarter of a mile of the tank at a height not greater than 500 feet...At the end of July tests with wireless telegraphy (i.e. morse code) proved successful, with messages being clearly received in the tanks from aeroplanes which were 9,000 yards away and at 2,500 feet altitude."
I'm hunting for some more references I'm sure I have somewhere, and will add to the above if I find them!