I think the plane would take off like normal, the wheels, which aren't connected to a drive train like they are with a car, would just be spinning an extra 75mph over normal takeoff speed while the velocity of the plane itself would be what it is normally. Thus, normal air moving under wings and normal lift for takeoff. The only effect might be some slight initial resistance from the rolling friction, but the thrust of a jet liner could easily overcome that.
Think of it this way... If you put a bicycle on this treadmill, then you would have no chance of riding it since the back wheel which is connected to the treadmill is required for propulsion. At 75mph you'd actually eat sh*t pretty bad. However, if you left the bicycle on the treadmill but you were standing off to the side of the treadmill holding onto it, you could easily push it forward at whatever speed you wanted to walk/run, because now the wheels are spinning freely and the propulsion system (you) isn't connected to the treadmill... the wheels would just be spinning really fast.