Why is this thread still going? Surely noone still thinks it will not take off.
Basically, for the frictional force between the treadmill and the plane's wheels to equal the force generated by the plane's thrusters, the treadmill will have to be moving many times faster then the plane. The reason for this is because airplane wheels are designed to have minimal friction (if minimising friction wasn't a design requirement the plane would simply rest on its undercarriage) and so a stationary, non-powered plane will not move back as far as the treadmill does when the treadmill is switched on. Anyone who disagrees with any of this is just wrong and making up an imaginary aerospace qualification will not change that (incidentally, I am an engineering student who has studied theory of flight). The plane takes off.
I have to admit thought that my initial reaction was that it wouldn't. This is a great riddle.