1. Yes. The air within the cockpit, although turbulent, will remain relatively stationary with reference to the aircraft.
2. Nothing can travel at the speed of light, therefore the question is meaningless. The theory that governs what light does relative to an observer (the train) is the same theory that dictates that the train could not achieve the speed of light. If you discard it to allow for the train travelling that fast, then you can't use it to describe anything else in the scenario.
3. Technically you could I suppose. However the weight of the aircraft would still be the same.