But, surely, if i understand this, the conveyor is going as fast as the plane should be going if it was moving, therefor keeping it still? It's just running on a running machine, there is no wind resistance or anything, and thats how a plane takes off, with the wind going by the wings and creating a vacuum. So it can't possibly take of, unless the riddle is twisted and saying the plane does actually move along the belt (like if you run on those belts at the airport when going to your terminal). So it won't take off, unless the riddle is a trick riddle and doesn't explain itself.