Factors such as temperature, weight, and even flight direction all determine the altitude of commercial aircraft.
Commercial aircraft typically fly at altitudes above 9,144m. (Photo: Flying Magazine)
The precise altitude of passenger aircraft at any given time during flight is influenced by several factors, including weight, temperature, weather, flight direction, and instructions from air traffic control. In most cases, passenger aircraft will fly at altitudes greater than 9,144m, according to John Cox, a former commercial pilot and director of the consulting firm Safety Operating Systems. Aircraft can reach heights of 12,192 to 12,496m, but such instances are relatively rare.
Tom Adcock, a former air traffic controller and director of safety and technology at the National Air Traffic Controllers Association (NATCA), has provided similar estimates. Boeing 757 and 767 aircraft can fly at altitudes of up to 12,802m and 13,106m, respectively. The Boeing 747-400 can fly even higher. Different types of aircraft have different maximum ceilings (maximum altitudes).
Air traffic controllers often consider the compass direction of the aircraft when advising pilots on altitude. Flights heading west are assigned even altitudes, such as 11,582m (38,000 feet), while flights heading east are assigned odd altitudes, like 11,887m (39,000 feet). This method ensures that aircraft moving in opposite directions maintain vertical separation. Aircraft flying northeast or southeast still operate at odd altitudes, while those heading northwest or southwest fly at even altitudes. However, if an aircraft is heading east at night and wishes to fly at an altitude of 9,754m (32,000 feet), the pilot may request it.
According to Cox, at higher altitudes, jet engines operate more efficiently with less air resistance. Pilots with this motivation consume less fuel as they aim to complete their flights with more reserve fuel, giving them more options in case of delays while airborne.
Flight management computers provide pilots with information on optimal and maximum altitudes based on weight and air temperature. Aircraft can ascend to higher altitudes after burning fuel and becoming lighter. The goal is to fly smoothly with less headwind when heading west, and climbing higher can assist pilots in achieving that.
