decrease sound emitted from jets when there is no exhaust or afterburner connected. right now jets are obnoxiously loud, but in real life turbine engines arent that loud. when the turbine engine of a helicopter is turned on, the rotor blade is way louder than the turbine itself, in stormworks its the opposite, same for turbofans. in my opinion jets should be a lot quieter, when a jet exhaust or afterburner is not connected.