How high do planes fly, and why up there?
How high do planes fly? A passenger jet spends most of its trip between 10 and 12 kilometres up — about 33,000 to 39,000 feet. That is roughly the height of Mount Everest stacked on top of itself, with a bit left over.
But “planes” covers a lot of very different machines, and they all sit at different heights.
The short answer, by kind of plane
| Kind of plane | Usual cruising height |
|---|---|
| Small propeller plane | 1–3 km (3,000–10,000 ft) |
| Airliner | 10–12 km (33,000–39,000 ft) |
| Private jet | 12–14 km (39,000–45,000 ft) |
| Fighter jet | up to about 15 km, briefly higher |
| Glider (no engine) | 1–3 km normally, much higher in mountain waves |
| Weather balloon | 30 km and up, which is higher than any of them |
Why they go so high
It is not for the view. There are four solid reasons, and they all come back to the same thing: the air up there is thin.
Thin air means less drag. Air pushes back on anything moving through it. Half as much air means about half as much push, so the plane can go faster on the same fuel. An airliner burns far less getting somewhere at 11 km than it would down low.
Weather mostly happens underneath. Clouds, rain and storms live in the bottom layer of the atmosphere. Climb above most of it and the ride is smoother.
Height is safety. If something goes wrong, height is time. A plane 11 km up can glide a very long way while the pilots sort it out — an airliner with both engines off still travels roughly 17 km forward for every 1 km it drops.
Fewer things to hit. Birds, hills and other aircraft are nearly all lower down.
Why they don’t go higher still
A wing works by pushing air downwards. Thin air is easier to move through, but there is also less of it to push. Climb far enough and the wing runs out of air to work with.
At the same time, engines need air to burn fuel. The higher you go, the less they can give you.
So every plane has a ceiling: the height where the wing can only just hold the plane up and the engines can only just keep it moving. Go past it and you simply cannot climb any more. For an airliner that is around 12–13 km, which is why they cruise a little below it.
The odd one out: flying with no engine
A glider has no engine at all, so none of the engine reasons apply. It stays up a completely different way: it finds air that is going up.
On a sunny day the ground warms unevenly. Air over the warm patches rises, sometimes in long bands with a little flat-bottomed cloud sitting on top of each one. A glider flies into that rising air, slows down, and goes up with it. Then it glides on to the next one, losing height all the way, and climbs again.
Gliders normally work between 1 and 3 km. But when strong wind pours over a mountain range it can set up a huge standing wave in the air, and gliders have ridden those waves to over 15 km — higher than an airliner, with no engine running.
Skimloft is a free browser game built on exactly this. You have no engine, so height is the only fuel you have, and flying forward spends it. You can see the rising air as specks of dust drifting upwards. Slow down inside it and you climb. It is one button, and it is the real trade that every glider pilot makes.
Quick answers
How high do planes fly in kilometres? Airliners cruise at 10–12 km. Small propeller planes stay at 1–3 km.
Why do planes fly at 35,000 feet? It is the sweet spot: high enough for thin air and smooth weather, low enough that the wing and engines still work well.
Can a plane fly higher than a glider? Usually, but not always. Gliders in mountain waves have climbed higher than airliners cruise.
How high can a plane go before the wing stops working? That height is called the ceiling. For an airliner it is around 12–13 km.
Want more? We wrote about the parts of an airplane and what each one does, and what angle of attack means — the thing that decides whether a wing is working at all.