Why Airliners Don’t Usually Fly At 43,000 Feet Unless Empty

Modern airliners are usually built with the ability to function when flying over 40,000 feet. Despite these capabilities, pilots don’t usually hit these levels when there are passengers are on board.

Plane above clouds
Despite being able to reach further heights, aircraft are usually flown at more reasonable levels. Photo: Kuster & Wildhaber Photography via Flickr

According to USA Today, a Boeing 767 has a service ceiling of 43,000 feet. The service ceiling is the maximum density altitude an airliner can reach according to its design. However, travelers are more likely find themselves in the air at a cruising altitude of around 35,000 feet.

Perfect height

Pilots often choose to fly at this level because this is the optimum height for commercial operations. Carriers avoid a massive amount of turbulence that would occur at lower levels. Along with this, most thunderstorms, severe weather incidents and birds can be avoided while above 35,000 feet. Also, the air is thin enough to reduce the aircraft’s drag, increasing its fuel efficiency.

There is also enough oxygen in the air here to combust with the jet fuel, generating enough power for the aircraft. A continued ascend will further reduce the amount of oxygen in the air, which may reduce the power generated. A higher elevation will require a longer climb, meaning the aircraft will burn more fuel in order to reach its cruising altitude.

Additionally, 35,000 feet gives more time for airline crew to address any unexpected mid-flight incidents. Aircraft can still land safely even if both engines fail, so this level maintains a balance of safety and efficiency.

Delta Air Lines B767-332
Airliners such as the Boeing 767 have the capability to reach 43,000. However, carriers often choose to operate at around 8,000 feet lower for operational purposes. Photo :Richard Snyder via Wikimedia Commons

Under pressure

Cabin pressure is not usually a factor that will prevent aircraft from operating at 43,000 feet. The internal pressure is maintained at 8,000 feet at this altitude, which is around the standard amount for most services.

Many business jets can travel even higher, at 50,000 feet, due to having large engines for the small size of the aircraft. The lighter weight enables these aircraft to climb higher more easily than larger jets with many passengers and materials.

Furthermore, Concorde could reach a maximum cruising altitude of 60,000 feet. The retired supersonic airliner’s turbojet engines were more efficient at a faster speed.

However, many light aircraft have to cruise below 10,000 feet because they don’t have the luxury of pressurized cabins like jetliners. These also may not have sufficient insulation to endure the cold temperatures higher up. Those that are built to endure the high levels don’t usually fly so high as they usually travel on shorter routes than their larger counterparts.

Concorde 1 94-9-5 kix
Concorde’s design enabled it to fly at greater heights than standard jet aircraft. Photo: Spaceaero2 via Wikimedia Commons

Wider impact

Meanwhile, high altitudes can impact airliners when it comes to taking off and landing. Earlier this year, Emirates announced a new route set to serve Mexico City. However, due to the airport’s altitude, the UAE based carrier can’t fly there directly. The Mexican capital’s airport has an altitude of 7,342 feet and some long-distance services can’t fly there directly.

This is due to the city’s climate and height changing the air density, causing the need for a longer runway for larger aircraft to operate on. Therefore, routes are often broken up using smaller aircraft along the way.

Altogether, commercial airliners have the physical capability to travel up to 43,000 feet. However, most of the time, it is not logical to operate at this elevation. There may be revolutions in engine technology, with new supersonic flights possibly being introduced in the future.

However, standard jetliners are still currently the most effective models for commercial travel. Do you think we will see any major aircraft evolution in the next decade?

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