Air acceleration

[maov]

I´ve been trying to tinker with air acceleration with no success, there is a function SetAccMult in OnRunOutOfFuel but no matter which input (tried 0.01, 100.0, -100.0 ) it does not seem to have any effect (SetSpeedMult works though so I must be doing something right). Does an AirUnit have an acceleration variable I can modify if nothing else or is changing the speed the only way to have an acceleration effect, when moving in a straight line?