In April 1915, Captain J.M. Furnival was the first person to hear a voice from the ground from Major Prince who said, “If you can hear me now, it will be the first time speech has ever been communicated to an airplane in flight.” In June 1915, the world’s first air-to-ground voice transmission took place at Brooklands, England over about 20 miles. Ground-to-air was initially by Morse code, but it is believed 2-way voice communications were available and installed by July 1915. By the early 1916, the Marconi Company (England) started production of air-to-ground radio transmitters/receivers which were used in the war over France.
The first time airplanes in-flight communicated with each other directly via radio was on September 2, 1916. This marks a historic advancement in the world of aviation, truly the one that has shaped the world of military and commercial aviation.
Link refers:
2-way radio
and a more detailed description of the history of air to ground comms can be found here:
A2G Radio
IG