[phayman53]

This does not work for piston engines, but one of the difficulties of making jet engines is the material for the turbine blades. They have to be extremely heat resistant because they are turned by the hot exhaust. You could have a world where highly heat resistant metals and alloys suitable for turbine blades are not available or invented. If that is the case, jets would be much harder to invent and much less efficient. In this case you could argue that extremely long range aircraft or heavy lift aircraft would be replaced by dirigibles. If you push this far enough, you could even claim that piston engines cannot be as powerful because of the lack of heat resistant metals, making heavy-lift prop aircraft impossible.