Generally, it is around 35,000 feet, but that can vary considerably depending on length of flight, weather conditions, air turbulence, and the location of other planes in the sky. Cruising speeds are about 550 miles per hour, although that too can vary considerably with headwinds, tailwinds, and other factors. These computer-based systems calculate the plane's position from its point of departure by closely tracking its heading, speed, and other factors after it leaves the gate. Some of the most sophisticated aircraft also are capable of using signals from a constellation of satellites to pinpoint their position. Satellites are expected to be the primary means of navigation in the future.
Pilots control and steer aircraft in flight by manipulating panels on the aircraft's wings and tail.
In this phase of a flight, the pilot gradually brings the aircraft back toward the ground by reducing engine power and speed, and thus the force of the lift. By this point, Air Traffic Control has put the aircraft in a sequence to land, carefully separating it from all other aircraft headed for, or leaving, the same airport. The landing gear is lowered on final approach, slowing the plane further. In addition, panels on the aircraft's wings are manipulated to increase drag and thus reduce speed and altitude. Aircraft generally are traveling at about 120 miles per hour relative to the ground when they touch down.