less oxegen levels and air pressure.
Most airplanes fly at high altitude because it is faster and safer as long as the cabin is pressurized. There is less clouds and turbulence. The airplane uses less fuel.
Higher altitude air is less dense. Less density means less air; less air means less friction, and less friction means a higher speed.
Because high altitude winds are faster.
At high altitude
yesclocks tick faster at high altitudes
One of the main reasons is to conserve fuel. Airplanes can fly at any altitude and speed. However, airplanes generally tend to fly at high altitude to conserve fuel. This makes the plane more efficient and keeps the operating cost down. Of course, an airplane can not always fly at max altitude at every flight. It may have too much weight or the distance it travels may be too short. So there is always a trade-off as to how they will fly the route.
Spaceships are MUCH faster than airplanes.
Yes, jets really are airplanes but they are faster airplanes.
36,000 feet
From 28,000 to 33,000 feet.
Yes.
Speed, altitude, and cost.