This is a BIG saftey adder if you don,t have a radio that does it ..I don,t believe the ama or anyone would care if this is on a plane or whatever..your better off with one than not having anything to take motor to idle or off... I have used them for years on prop planes without any problems... so like i said, if someone has an older radio ,or can,t afford a good one, this works great..its nice having a good radio but not everyone can afford one ...this is for the guys who can,t or just can,t see putting out that much money..... i think the only reason some of the mfgs. say not for a/c use is for thier own liability,due to fatal accidents being a lot more possible with a/c....[imho] every plane should have fail-safe engine shut down at least to idle..I think we all can see the safety benefits of that..