I realize this is is a somewhat old thread, but since it's been resurrected anyway...
Something you have to remember is that the airplane (or balloon, or whatever) would have to take off from the earth, which is already moving. This gives the object the same movement. It is the same as if you are walking down a sidewalk and toss a ball straight up in the air, from your perspective. From your point of view, the ball goes straight up and comes straight back to your hands. It does not land behind you. However, from a bystander's point of view, the ball appears to have a parabolic trajectory. It is easy to see that the movement is there as soon as the object "takes off", and it will always have that same forward movement unless another force acts upon it in a different direction, which defeats the whole purpose of this idea.