Better fuel economy. The air is thinner at higher altitudes.
An average plane flies between 5 to 10 km above the surface of the earth. Planes cannot fly below or above the altitude. After this altitude there is not much air.
They usually fly in the stratosphere. That is from 25,000 feet to 40,000 feet. This may differ from palne to plane. A plane like Cessna flies very close to the ground at about 9000 feet.
1000 - 500 ft
They usually fly at an altitude of 30,000 to 35,000 feet, to avoid bad weather.
Helicopters fly at low altitude.Passenger planes climb to high altitude.Birds use low altitude height to fly from tree to housetop.Military cargo planes pass over my house at low altitude.
The ceiling height of a Cessna 172 is 13,500 ft. The optimum altitude for maximum range is 12,000 ft.
There is no certain cruising altitude for a commercial airline. it depends on where they are flying and how long they fly. most airlines fly above 10,000 ft. the max altitude is around 41,000 ft.
Flying at altitude
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.
To be able to fly in a plane, you have to be at a much higher altitude, and not in the same atmosphere conditions as the kind we are exposed to. There is lots of scientific research behind this, but to be sure you find what you are looking for, google it and find a reliable source to tell you! :)
A 747 can fly at 33,000 feet or 6.27miles high.
Usually we fly in a plane.