2024-08-03 19:20:36
“In most cases, airliners fly at an average altitude of 30,000 feet (9.1 km),” says John Cox, a retired commercial airline pilot who now runs consulting firm Safety Operating Systems. “They can go as high as 40,000 to 41,000 feet (12.2 to 12.5 km), but this is relatively rare.”
Retired air traffic controller Tom Adcock, now director of safety and technology for the US National Air Traffic Controllers Association (NATCA), offers a similar assessment, saying that most flights are above 30,000 feet (9.1 km) and some of they reach heights of 41,000 (12.5 km) or 43,000 (13.1 km).
For example, the Boeing 757 can fly up to 42,000 feet (12.8 km), the Boeing 767 up to 43,000 (13.1 km), and the Boeing 747-400 even higher. Different types of aircraft have different maximum allowable limits.
When giving the altitude to the pilot, the controllers take into account the direction in which the aircraft is flying. Although altitudes such as 38,000 feet (11.6 km) and 39,000 feet (11.9 km) are even numbers, “38” is even and “39” is odd. Even numbers like 38,000 feet are given for westbound flights, and odd numbers like 39,000 feet are given for eastbound flights.
In this way, aircraft flying in opposite directions have a fixed vertical distance between them. Aircraft flying northeast or southeast will still fly at odd altitude, while aircraft flying northwest or southwest will still fly at even altitude.
“There are exceptions,” Cox notes, noting that, hypothetically, if he were flying east at night and wanted to fly at 32,000 feet (9.8 km), he would still request that from air traffic control.
Determining the exact altitude an aircraft is at at any given time involves a number of variables, and the former pilot says that generally higher altitude is better. “At higher altitudes, jet engines work more efficiently and there is less air resistance. The pilot is encouraged to burn less fuel,” says Mr Cox.
According to him, this rule also applies during short flights. “You will be surprised – but even during short flights it is the most efficient [degalų] the way to use it is to take the plane to a high altitude, reduce the power and start the descent again,” says Mr Cox.
The flight control system provides the pilot with information about the optimal flight altitude of the aircraft, as well as the maximum altitude, taking into account the weight of the aircraft and air temperature. An airplane can go higher as it burns fuel and becomes lighter.
“Pilots stay as close to the optimum or maximum altitude as possible,” says Mr Cox. However, an air traffic controller may ask the pilot of the aircraft to climb to a higher altitude than the aircraft is currently capable of reaching, in which case the pilot will have to decline such a request.
Commercial airliners aren’t the only planes in the sky. A Cessna 172 small plane pilot will fly below 10,000 feet (3 km), a commercial turboprop will fly higher than these aircraft but lower than jets – for example, the Bombardier Q400 operated by Alaska Airlines is not designed to fly above 25,000 feet (7.6 km), Adcock says.
People fly the highest in private jets: Learjets and Gulfstreams routinely fly at altitudes of about 45,000 feet (13.7 km) and above, and can climb as high as 51,000 feet (15.5 km).
Adapted from Popular Science.
2024-08-03 19:20:36