what height do planes fly

Commercial planes fly at different altitudes depending on various factors such as the type of aircraft, the distance it is traveling, the type of engine it has, the weight of the aircraft, and the current strength of the winds. The cruising altitude for most commercial airplanes is between 31,000 and 42,000 feet, or between about 5.9 to 7.2 miles high. The exact height chosen for a given flight will also depend on wind conditions, and pilots may need to adjust their altitude to take advantage of or minimize the adverse effects of high-altitude jet stream winds. The main reasons for flying at high altitudes are to avoid other planes, reduce the risk of crashing into mountains, not collide with birds, avoid turbulence, and maximize fuel efficiency. Smaller aircraft, whether commercially operated or not, will fly at lower altitudes, often below 15,000 feet, due to the type of engine they have, which makes them unable to reach the same heights.