To dream that a plane crashes signifies that you have set overly high and unrealistic goals for yourself. You are in danger of having those goals come crashing down. Alternatively, the crashing airplane represents your lack of confidence, self-defeating attitude and self-doubt. You do not believe in your own ability to achieve those goals. Loss of power and uncertainty in achieving your goals are also signified.
To wake up before you crash in your dream may simply be the anticipation of the crash that jolts you awake. It is similar to the notion of waking up before you hit the ground from a fall.