Comment by pieterbreed

Well, I don't have any material on it but you can see that it makes sense from a mechanical physics point of view. Load up a craft to maximum possible weight (with ballast even) Then fly as high and is fast as you can (during which you build up the maximum achievable potential and kinetic energy) then during a dive build up as much speed as you can (during which you convert your potential energy from the weight and height of the craft into more kinetic energy) as you level out, you dump the excess weight and start climbing. Since you now have less weight but the same kinetic energy, you are free to take your craft higher than the height from which it started to descend.