Lacking the engine thrust to extricate the aircraft from a perilous condition, usually a stall. For the highest performance aircraft this is a virtual impossibility, as they can accelerate vertically. In a sense, every aircraft is absolutely behind the power curve as it begins its takeoff roll. As its speed gathers and the wings develop lift, the aircraft enters the normal operating regime or 'envelope' of the power curve. It's a little like you must carefully husband your momentum when driving your car in snowy, icy conditions. When you lose enough momentum, all the power in the world cannot rehabilitate an out-of-control skid. Also see: coffin corner.