At what height do airplanes fly?

Sometimes looking up into the sky, we see a tiny silhouette of an airplane flying somewhere in the altitude. I wonder, but at what height do airplanes fly?

It is necessary to say at once that the cruising speedThe flight of an airplane and the height of its flight are very tightly connected. The density of air and, consequently, its resistance at different heights - are also different.

Hence, simple mathematical actionswe find that at a speed of 900 km / h (this is the cruising speed for passenger airliners), the optimal, in terms of the ratio of air resistance, lift (for fuel economy) will be about 9-10 thousand meters. For "Concorde" with its speed of 2500 km / h, an altitude of 20 thousand meters is perfect.

That is, we get that the main indicator is the saving of money, weather and security are secondary.

Military aircraft, as a rule, do not fly higherthe mark is 11-12 thousand meters, although this is possible, although for different purposes the flights of military aircraft are set their goals, for each goal is set its own height.

Light aircraft fly at altitudes usually no more than 2,000 meters, their speed during the flight does not exceed 300 km / h.

Cargo planes fly on the sameheights, as the passenger. The altitude of the flight for them is calculated in such a way as to minimize the costs, however, the situation is similar to civil aviation.