.... this is insane. In some backward authoritarian state I could imagine this, but in Europe?? Every person who owns a camera in the UK needs to be out on the street photographing everything in sight. Some well directed civil disobedience is well in order to stop this madness.

"monorail, Monorail, MONOrail, MONORAIL!!!

Well, sir, there's nothing on earth
Like a genuine,
Bona fide,
Electrified,
Six-car
Monorail!
What'd I say?

Monorail!!"

Someone had to say it.

Granted this was a while back, but apropos still. Someone a little ways a head of me had their peanut butter and jelly sandwich confiscated. I had visions of someone holding up their lunch and flicking a lighter underneath it. I was so glad to have been saved from the possible exploding jelly.

I was soon after told by a ticket agent that earlier that same day an air marshal had had his toothpaste confiscated. But he was allowed on the plane with his gun. Again, a feeling of well being over took me, mostly because I knew that obviously people of imposing intelligence were running the show.

Oh what a world it seems we live in....

Ok, I'm sitting at home with the flu (not bird flu, don't worry), and I have to respond to this, it's too disturbing not to.

The plane won't take off. Thrust, relative ground speed, whatever, it needs LIFT to take off. We must overcome the force of gravity holding the plane on the ground. That lift comes from air moving over and under the airfoil wing. THE WING. It doesn't matter how fast the wheels are moving, if the air is not flowing over the wing (both sides) then it won't take off. The plane must be moving in relation to the air (or the air in relation to the wing, however you want to look at it) for it to take off. It seems quite clear in the question that the conveyor belt is undoing any of the forward momentum created by the propulsion.

And the tires would not accelerate infinitely, they would only go as fast as the force pushing it, so no burning rubber, no molten treadmill. If you're getting enough thrust to move the plane 100mph (looks like they're using an ultralight for the show, they won't get 100mph out of that) then the wheels will be moving at 100mph. That's the point of the question; the treadmill and the thrust cancel each other out. To discuss at which point the tires will burn out (which will only send the plane BACKWARD as the treadmill continues on its merry way, taking the plane with it now, which is also what would happen if you put the breaks on, #114) is to miss the point of the question and try to get around the answer on a hypothetical technicality. And it still doesn't take off in any case, it goes hurtling backward, quite violently.

The argument that the treadmill itself will cause drag on the air, causing wind, causing the plane to take off is partially correct. There will be a breeze, but again especially with the low speed of an ultralight you're not going to get the movement of a sufficient mass of air by the treadmill to create the airfoil. If the plane did get buffeted into the air (which I don't see as the same as flying, much like getting under a little plastic balloon and blowing it up in the air doesn't constitute flight) by the breeze from the treadmill (an ultralight might get buffeted into the air, as it's, well, ultra light) I would be greatly surprised if it was able to gain enough airspeed to say airborne, since now it's moving out of the wind from the treadmill and has to power itself through the air, which it can now do as it's free of the counter effects of the treadmill. It would stall and fall back to the treadmill though, it needs more "runway" to gain speed. That's not "taking off" in my book, any more than me hopping into the air is me about to take flight.

A quick example of a similar problem; I asked a student of mine (I teach the kids the music) what would happen if while she were ridding along on an airport conveyor belt she jumped into the air. She said she would land behind where she jumped. I tried to explain that she's wrong, and she would not have any of it. She was a stubborn 13 year old, it was to be expected. She would land exactly where she started, unless she created quite a bit of air drag. The air drag is the only variable in that equation, and unless that conveyor belt is flyin, there's not going to be enough to worry about.

So, in summary; no airspeed over the wings = no overcoming gravity = no flight. The treadmill will only go as fast as force of the propulsion is pushing it. If it was a rocket on the Moon, on a treadmill, and the vector of the rocket was not directed sufficiently opposed to the pull of the Moon's gravity (small though it may be), it will not take off. If on Wednesday the little thing takes flight, I will eat crow and be very curious as to why it took off. If it doesn't take off, I am going to be ashamed that physics professors argued so vehemently that it would.

PS I couldn't read all the posts, hopefully I didn't repeat what too many others have said.