Just a s quick simple suggestion for the next update since rocket planes (or more to the point, rocket "powered" planes) have existed throughout history.

Possible differences between a solid rocket engine vs a jet engine (in game):
-Pound for pound a rocket engine could be twice as powerful as a similarly sized jet engine.
-Requires no air-intake.
-Carries it's own fuel.
-Once ignited the engine cannot be shutdown and runs at full power until it burns through it's fuel.
-Burn-time is around 30 sec. Longer if multiple engines are "stacked" end to end (no nudging one inside of another).