We all know that wing-propeller planes rely on air to create a thrust. They suck the air in and push them back hard that it's opposite reaction pushes the plane (Newton's law).

Does that mean wing-propeller struggles up at high altitude because of the low pressure of the air ?

Same question for jet engine.

  • $\begingroup$ Think about it a bit: low air pressure implies major loss of lift, not to mention oxygen-starving the engine, in addition to thrust loss. $\endgroup$ Apr 1, 2014 at 16:58

2 Answers 2


Yes it's called the absolute ceiling. This is the highest altitude at which an aircraft can sustain level flight. When a plane reaches this height the thrust of the engines at full power is equal to the total drag at minimum drag speed. This occurs where the maximum thrust available equals the minimum thrust required, so the altitude where the maximum sustained (with no decreasing airspeed) rate of climb is zero.

The service ceiling is lower and has some safety margin built in. This is the height where the rate of climb is not zero so the craft still has some maneuverability. Most commercial jetliners have a service (or certificated) ceiling of about 42,000 feet and some business jets about 51,000 feet. Many military jets are able to fly substanitally higher but it is classified. The SR71 in 1976 published a world record 85,135 feet, however I'm sure they and some others can go higher.

All propeller based aircraft have much lower ceilings and they vary widely with design of the craft. The Turboprop aircraft with the highest altitude ceiling is the Lockheed P-3 ORION, which has a maximum cruise altitude of 55,000 ft.

There is a trade off point because as the air gets less dense the plane can travel faster. So many planes climb to the 20,000+ height for less drag but still enough pressure for efficient thrust.

  • $\begingroup$ Does the same apply to fish swimming in deep vs closer to the surface ? $\endgroup$
    – fahadash
    Apr 1, 2014 at 20:02
  • 1
    $\begingroup$ @fahadash fluids do not compress like gases. density of the ocean varies more with temperature and salinity, but that variation is small. $\endgroup$
    – user6972
    Apr 1, 2014 at 20:11
  • $\begingroup$ Check this: Flying over Mt Everest - a plane over the Himalayas. Now you look it up: 9N-AHV. Could that be correct? A propeller plane at that altitude? Service ceiling: 7900m - on one engine: 4572m: en.wikipedia.org/wiki/… - doesn't sound good? How high is the Tibetan Plateau on average? $\endgroup$ Apr 20, 2021 at 15:41
  • $\begingroup$ Tibetan Plateau: "...average elevation exceeding 4,500 metres (14,800 ft)". $\endgroup$ Apr 20, 2021 at 15:47

In normal subsonic flying, as air gets thinner, it means there is less lift but also less drag, which can be made up for by going at a higher speed. So to get maximum range and speed, planes fly as high as possible. (Other factors may weigh against this, such as headwinds being faster at higher altitude.)

Piston engines generally require turbochargers at high altitude, because there's less partial pressure of O2. (Turbine engines are turbochargers.)

In terms of range for given fuel, it is well-discussed here. Just note that

Jet engines are characterized by a thrust specific fuel consumption, so that rate of fuel flow is proportional to drag, rather than power.

The other thing that happens is aircraft can come up against the Q-corner. This means that, while with a given indicated air speed, they are actually going faster because the air is thinner, the speed of sound actually decreases with altitude. Since subsonic aircraft must stay well below Mach 1, it means as they go higher they must also reduce indicated airspeed. When they get caught with a very little span between Mach 1 and stall speed (minimum flyable indicated air speed), then they are in the Q-corner. This limits commercial craft to the range of around 40kft altitude.

The way the U2 spy plane can get up to 60kft is by having a much lower stall speed. It has long, narrow wings like a glider. Even so, it routinely flies in its Q-corner, and care must be taken in turns, because the "outer wing" may overspeed at the same time as the "inner wing" stalls.


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