The fluid dynamics behind bumblebees' flight are different from those that allow a plane to fly. An airplane's wing forces air down, which in turn pushes the wing (and the plane it's attached to) upward. For bugs, it isn't so simple. The wing sweeping is a bit like a partial spin of a "somewhat crappy" helicopter propeller, Dickinson said, but the angle to the wing also creates vortices in the airlike small hurricanes. The eyes of those mini-hurricanes have lower pressure than the surrounding air, so, keeping those eddies of air above its wings helps the bee stay aloft.