Motorcycles are reaching new heights.

Apparently, there are some people out there who like to build planes. We’re not talking Boeing or Bombardier here—I’m talking about Joe Something building his own rig in the barn at the back of his house.

While car engines seem to be better adapted to the requirements of a plane—considering not everyone has a jet engine in their backyard—some homebuilders get a little bolder with their creations. They choose to adapt motorcycle engines to make their lightweights fly. Here are four really cool, motorcycle engine-propelled planes.