NY - the question said nothing about the plane's ability/inability to move forward relative a point off of the belt.

If it was anchored and unable to move forward (again, relative to a point off of the belt), then you are right - try as you might if you don't move you won't fly.

If it is able to move relative to a point off the belt, then it would be moving thru the air, and able to attain lift. It would be moving down the conveyor belt runway away from the plane's starting point and toward the belt's "head pulley"; therefor the fluid air will be moving over the wings, and able to attain lift. This is the assumption I made, and as it was not stated otherwise, the assumption I will follow.

Edit to add: (Just thought of this) If the plane was anchored the belt would never start moving, because the plane would never start moving, because the wheels would never start turning, because they are obviously not driven by jet engines.