Modern passenger planes can fly at various heights. Seeing the flying by plane behind which there is a white trace in the sky, we often do not think as highly it flies.
At what height do passenger planes fly?
The majority of airliners fly at the height from 10 to 12 thousand meters above the ground today. They come to such height approximately in 20 minutes of flight. Such choice of height depends on characteristic of the atmosphere on it. Air at the height more than 10 thousand meters very discharged that allows to spend less fuel for overcoming front resistance. But at the same time it has enough oxygen for maintenance of continuous combustion of aviation kerosene.
The choice of height depends not on desire of the commander of the aircraft, and is defined by dispatching service and depends on weather, wind speed at the earth and on the direction of flight of the plane. Height at which the plane flies is called a flight echelon. Uniform echelons for flights are around the world accepted and they cannot change depending on the country over which the plane flies. If flight of the plane takes place from the West on the East, then for it only odd echelons (35, 37, 39 thousand feet) are provided. If the aircraft flies to the West, then echelons for it will be , on the contrary, even (30, 36, 40 thousand feet).
Also height in 10-12 thousand meters is caused by lack of birds. Birds do huge harm to aircrafts, facing them at small heights. At big heights there is no such danger.
At what height do military aircraft fly?
Military aircraft fly with greater speed, than passenger planes. Height more than 13 thousand meters are suitable for supersonic flights of military aircraft. At such heights density of air is very low and it is much easier to reach acoustic speed, than at the height below 13 thousand kilometers. For some fighting tasks the modern military aircraft can get on height more than 25 thousand kilometers. The record of the maximum flight altitude belongs to the domestic MiG-25 aircraft and makes 37650 meters.