The stratosphere, which is the second major level of the Earth’s atmosphere, is just above the troposphere and below the mesosphere.
Whether an aircraft flies in the stratosphere or not largely depends on the type of aircraft. Some airplanes are better suited to flying at higher altitudes and it is also more advantageous for them to do so.
Light Aircraft vs. Private Aircraft vs. Commercial Aircraft
You won’t find any light aircraft flying in the stratosphere. This is because they lack pressurized cabins and are unable to operate at higher altitudes.
Light aircraft stick to the troposphere and within an altitude range of about 10,000 feet.
Commercial aircraft, on the other hand, as well as private aircraft like private jets, actually prefer to fly in the stratosphere due to the several benefits flying at such an altitude brings.
3 Reasons Why Airplanes Fly in the Stratosphere
An airplane flying in the stratosphere uses far less fuel than at lower altitudes thanks to the lower air density and lower temperature.
The air temperature drops 2°C or 35.6 Fahrenheit for every 1,000 feet an airplane climbs – up to about 36,000 feet. This results in big savings for the airline and other operators.
As much of the weather phenomenon we see on Earth occurs in the troposphere, an airplane flying in the stratosphere can avoid the bad weather that is typically found lower in the atmosphere.
However, this isn’t necessarily always the case.
Variations in the jet stream and other local wind shears – i.e. the difference in relative speed between two adjacent air masses – can also cause clear-air turbulence (CAT) in the stratosphere too.
If you’ve wondered why you don’t see any clouds in the stratosphere it’s because the air contains very little water vapor, so clouds are unable to form.
The exception is polar stratospheric clouds, which are found near the poles in winter in the lower stratosphere.
At higher altitudes, the air is thinner (roughly thousands of times thinner at the top of the stratosphere compared to at sea level), which results in less drag.
An airplane flying in the stratosphere can therefore fly faster, and a pilot will reach their destination more quickly.
This is particularly important for commercial flights where a strict schedule must be adhered to in order to avoid delays.
Are There Any Airplanes That Fly Higher Than the Stratosphere?
Airplanes do not fly any higher than the stratosphere.
In regards to commercial flight, when Concorde was still in operation, its maximum cruising altitude was 60,000 feet.
For military aircraft, in 1976, the Lockheed SR-71 set the record for the highest altitude achieved in horizontal flight at 85,069 feet.
Today, the highest altitude commercial airliners will operate at is about 45,000 feet.
The maximum altitude business jets will fly is about 51,000 feet.
Why Don’t Airplanes Fly Higher Than the Stratosphere?
Airplanes don’t fly any higher than the stratosphere and into the mesosphere or beyond for three main reasons.
As air density is so low, it is very challenging for an airplane’s wings to produce adequate lift, and adequate thrust also cannot be generated.
Additionally, due to air pressure at very high altitudes being so low, the cabin would have to be pressurized to such a high level that it would have an effect on the weight of an aircraft, thereby requiring it to generate even more lift and thrust.