Commercial or passenger aircraft are usually designed for optimum performance at their cruise speed or VC. Combustion engines have an optimum efficiency level for fuel consumption and power output. Generally, piston engines are most efficient between idle speed and 25% short of full throttle.
The blood to your head rushes when you do a quick movement, so, naturally, dizziness is expected. I think the blood rushes from your head too fast. it is called postural hypotension.. whereby, due to getting up suddenly to a upright position, there is lower blood supply to th head.
If you tend to get light-headed when you stand up: 1  Avoid sudden changes in posture. 2  Get up from a lying position slowly, and stay seated for a few moments before standing. 3  When standing, make sure you have something to hold on to.