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.
In fact, getting the blood pressure down this much in very old people has not been found to reduce their risk of dying. In addition, many individuals over the age of 65 may feel dizzy, fall or pass out when they stand suddenly due to blood pressure that is suddenly too low. This condition, known as postural or orthostatic hypotension, poses a danger of fractures and other serious injury.