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.
this is why you get light headed when you are sitting and stand all of a sudden because when you are sitting your blood tends to pool up in your legs and standing all of a sudden sends a sudden huge burst of a lot of blood to your brain. your brain gets a little oxygen starved when you are sitting. Source(s):