English as the Lingua Franca of global ATC.
I'm currently researching the early development of aviation apropos current practices and would like to know if anyone could provide me with the definitive reason behind why English is the (generally) accepted lingua franca of ATC around the world. Is it merely that English is more widely spoken by aviation professionals, or is there some mutually agreed upon convention that renders it so? Responses with sourced references would be particularly welcome.
Many thanks,
Leo.