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.
Patients who have trouble with dizziness and/or syncope when standing may suffer from hypotensive orthostatic intolerance. They are fine when sitting but when standing the vascular tone and cardiac output decreases and the BP and HR go down resulting in dizziness/syncope.