[emeritus]

Here's an extract from the chapter in the first edition (1942) of "Principles of Aeronautical Radio Engineering" by P.C. Sandretto that discusses the then about-to-be-introduced VHF radio system. Apparently both AM and FM were trialled, but it was found in comparative tests that FM offered no significant advantage. AM was chosen to get the system up and running with minimal technical risk, but it was envisaged that FM might be used in the future " should frequency modulation prove, upon further tests, to have outstanding advantages.".