Scientists and engineers tested a prototype Mars robotic plane part of The Mother Goose mission. The Mother Goose plane is basically an 8 foot remotely operated wing that can do some pretty amazing things like a near zero velocity landing. Someday the plane will be much larger sporting a 65 foot wingspan, inflatable with a fold-up propeller. Then it will become more like a UAV autonomous robot for flying around mars, that can even land, or even drop tiny robots or instruments.
However, some people seem to think that flying on Mars is much more tricky.