interesting argument.. (for the self proclaimed geniuses of IA)

[Ruiner]

On one hand I want to say the headwind will actually push the 747 back keeping it on the conveyor BUT that same headwind could aid it in taking off.. even if the plane was not moving.

So I'll go with yes, it will still take off.

Actually, it will appear to "hover" in the air and not move forward or backwards if the wind is strong enough to keep it from going forward, but weak enough to not push it back. I know this because I have flown RC planes into strong headwinds and seen this effect with my own eyes.

[ISAtlanta300]

After some research on the original question, it will indeed take off. The wheels will just be moving at twice the speed of the conveyor......

[Ruiner]

The wheels will just be moving at twice the speed of the conveyor......

No. The plane can still move forward and the wheels still spin backwards. Keep in mind that the wheels roll free. They really have no bearing on the plane's movement when all is said and done. The wheels can move backwards at 1000mph while the plane pushes forwards. The plane doesn't care. That is, of course, assuming that the wheel-brake isn't on.