The Risks Of Flying Too High (2024)

While passengers may not realize how high the aircraft is flying or should fly, all aircraft are limited by the altitude they can climb to and fly at. That, in aviation terms, is called service ceiling. Airframes are designed to withstand a certain altitude and the surrounding environment. Similarly, jet engines' performance is limited by a specific altitude beyond which the performance deteriorates.

So, can aircraft fly beyond their limit? What could happen to the airframe and engines if an altitude greater than the designed service ceiling is attempted? This article explores early-age flights and how cruising altitudes have changed over the years. The article also focuses on the airframe and engine performance risks of flying too high.

Planes were used extensively during WWI

In 1911, Italy became the first country to incorporate planes into the military during the Turkish-Italian war. During the First World War, all sides used planes extensively for reconnaissance, bombing, and engaging enemy aircraft. At the time, the aircraft could only operate during daylight hours as the pilots relied on ground references to know where they were.

Photo: USLibrary of Congress | Wikimedia Commons.

In June 1919, Alco*ck and Brown took off from St. John's, Newfoundland and flew nonstop for 16 hours before crashing in a bog in Western Ireland. For the record-breaking Atlantic crossing, the converted Vickers bomber never flew higher than 12,000 feet, so there was enough oxygen in the air for the pilots to breathe. A decade later, Charles Lindbergh and Amelia Earhart became worldwide celebrities, setting records of their own.

The Boeing 307 was the first pressurized airliner

The next massive revelation occurred in 1937 when the US Army Air Corps began work on the X-35, a modified Lockheed Electra with a pressurized cabin. A year later, Boeing released the Boeing 307 Stratoliner, a passenger aircraft that could fly at 20,000 feet.

Photo: D. Miller | Wikimedia Commons.

The advantage to flying at higher altitudes was that the higher you got, the thinner the air was, making the plane more economical to operate. The ability to fly above the clouds also allowed pilots to avoid storms and other bad weather.

In 1949, the world was introduced to the first passenger jet airliner, the British-manufactured de Havilland Comet. Unfortunately, the plane had some design issues and had to be grounded for two years following fatal crashes. Nevertheless, it showed the world that passenger jet travel was possible.

Boeing ran with the concept of jet airliners and, in the late 50s, debuted the Boeing 707. By the time various variants had been built, the Boeing 707 had a maximum ceiling of 42,000 ft (12,800 m), which is where we are today.

Concorde was the exception

Because the Concorde could climb and descend fast and had engines that worked in very thin air, it could fly at 60,000 but tended to cruise at an altitude of around 50,000. Other airliners would struggle to do that as there is insufficient oxygen to power the engines.

Photo: John Selway | Shutterstock

The sweet spot for modern airliners is between 35,000 and 42,000 feet, where the plane's engines are most efficient. The way the wings are designed is also unsuitable for thin-air flight as they would not be able to create enough lift. Planes cannot just keep going up and up - at some point, they will stall.

Limitations to altitude

Basically, commercial airliners cannot fly higher than their maximum rated ceiling because of the following three factors:

• Engine thrust: At higher altitudes where the air is thin (less dense than at lower altitudes), there is not enough air to pass through the engine for it to create the required thrust needed to keep the plane flying. The density of the air is also affected by temperature. This means the aircraft's maximum altitude on hotter days is much lower than on colder days. The aircraft's maximum altitude is when it reaches a point when it can no longer create enough thrust to keep climbing at least 300 feet per minute.

• Cabin pressure differential: At high altitudes, the passengers would not be able to breathe if they were not in a pressurized cabin. The higher the altitude, the higher the air pressure differential between the inside and outside of the plane. At around 43,000 feet, a maximum of 9 PSI is reached, and anything higher could lead to a catastrophic structural failure of the aircraft.

• Aerodynamic altitude: If a commercial airliner flies too high, it will encounter less dense air passing over the wings to create lift. This can cause the plane to stall and fall out of control. Depending on the weather conditions and aircraft weight, this can occur anywhere between 40,000 and 45,000 feet.

Photo: Luke Peters | Simple Flying

All airline pilots are trained to know the capabilities of the planes they are flying and ensure that everything is kept within safe margins. In 2004, Pinnacle Airlines flight 3701 crashed after the two pilots repositioning the Bombardier CRJ200 decided to see how high the plane could go.

After the plane reached 41,000 feet, its max ceiling, both engines failed. The pilots tried to restart the engines but could not before the aircraft crashed near Jefferson City Memorial Airport (JEF) in Missouri.

What are your thoughts on how high airplanes can fly and possible consequences of flying beyond the design limit? Share your opinion in the comments section.