[aerodude]

Gonna comment on your last statement here. The reason aircraft cruise so high is because 1) it's efficient. Flight paths are heavily optimized, and while you spend energy getting up there, you don't spend much getting down. Energy is a conserved quantity. 2) We want to fly above the weather. In the early days of flight, we actually did fly at low altitudes, and we lost a lot of aircraft in the process. Low altitude flying is dangerous, and not really an advantage. Generally, you want more altitude, not less, because the more altitude you have, the more energy you have. This let's you trade height for speed, keeps you away from weather patterns, and means that in the event of a failure, you have time to plan and execute.