My electric rc airplane throttle channel does not work, What is the problem?

It could be any number of things:

The radio's throttle trim (if it's a computer radio) might be so out-of-whack that it will not turn the motor. The speed control might be fried. The motor itself could be burned up. It's more than likely the speed control. That's the only problem I've ever had where the plane wouldn't throttle up.

Go on www.rcgroups.com and search the forums. You'll find your answer there.