My understanding is that kinetic energy is the work done to accelerate the mass of the a/c. This is increased by engine thrust or trading potential energy (losing altitude and claiming the acceleration from gravity). If you have low PE and low KE then total energy is low which is very dangerous.

It's a while since I did A Level Physics but here goes:-

Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. The energy is stored as the result of the gravitational attraction of the Earth for the object.

So the higher you are (above earth) the more the potential energy?

Kinetic energy is the energy of motion. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy.

KE = 0.5 m (V)squared - where m is mass and V is speed. Double the speed and you quadruple the energy.