http://www.youtube.com/watch?feature...&v=zys3igBmhB8

It was an April Fool's prank.

There's a fishing line between both fans, upon which the plane rests.

I expect that this works for the same reason that a very light ball can hover motionless over a fan blowing vertically upward. According to Bernoulli, a moving mass of air exerts lower pressure. If the ball moves a bit out of the center of the air stream, a higher pressure is exerted on the side of the ball that is toward the outside of the air stream, and a lower pressure on the side of the ball that is closer to the center of the stream. This tends to move the ball back to the air stream's center. However, I don't know for sure if this explains the hovering paper airplane.

Re-read post two. It's true. Google it. <div>
</div><div>Tough to refute a prank with a bunch of theories.  </div>