Hey alfonz1986, based on people's question and response, I think part of your phrasing of the question caused some confusion. Having seen the Mythbuster episode (well I've seen all of them from the beginning, and yeah, most of what they feature have to start off as a relatively well-known myth first, so the myth pretty much always outdates the corresponding TV episode), let me rephrase your puzzle to precisely describe the situation demonstrated on that episode (unless you purposely intended for your puzzle to differ from the myth as presented on TV):
[edit: completely rephrase again after Johannes corrected some fundamental misceptions I have around the setup of the scenario]
Imagine two absolutely identical airplanes. Airplane "A" sits on a normal runway, while "B" sits on a giant conveyor belt. We now start and turn up both airplane's propellers at completely matching rates at all times. Obviously, A will start to move forward and eventually lift off.
Now imagine that with B, while we are ramping up its propellers at matching rate with A, we also have the conveyor belt turned on, and its speed ramp up at a rate always matching the speed of A, but going backwards. What will happen with airplane B? Can it takeoff or not, and why?