My suggestion to simpleplanes is engine emergencies.
Basically, engines and all moving parts can break down slowly.
Engines need oil to fly more efficiently
Engines have afterburners that increase the temperature of the engine. Engines randomly lose power, fuel and oxygen. This can be fixed with a new part that fixes all parts on your plane while you fly. Damaged engines need to be switched off to be fixed or can be flown on if needed to.