How high do planes fly?
Most airliners cruise between 31,000 and 42,000 feet — roughly 9.5 to 12.8 km — and settle around 35,000 to 40,000 feet on a long flight. Through the air they do about Mach 0.78 to 0.85, near 900 km/h. Over the ground they do whatever the wind allows, which is why the same route takes longer one way than the other.
The cruising altitude, by aircraft
A jet climbs until the air is thin enough to be worth the trouble. At 36,000 feet the air is about a quarter as dense as it is at sea level, so the same airframe pushes through a quarter of the resistance and burns a fraction of the fuel. You are also above almost all the weather.
It does not climb further than that because the engines still need air to breathe, and because the gap between the slowest the aircraft can fly and the fastest it may fly narrows the higher it goes. Every airframe has a ceiling where that gap closes.
Aircraft rarely sit at one level the whole way either. A long flight burns off tonnes of fuel and gets lighter as it goes, so it steps up — starting near 33,000 feet and finishing closer to 39,000 without you noticing a thing.
| Aircraft | Typical cruise | Ceiling |
|---|---|---|
| A320 family | 35,000–39,000 ft | 39,800 ft |
| Boeing 737 | 35,000–39,000 ft | 41,000 ft |
| Boeing 787 / A350 | 37,000–41,000 ft | 43,100 ft |
| Airbus A380 | 35,000–41,000 ft | 43,000 ft |
| ATR 72 / Dash 8 turboprop | 17,000–25,000 ft | 25,000 ft |
| Gulfstream G650 business jet | 41,000–49,000 ft | 51,000 ft |
Why the altitude is never a round number
Above 29,000 feet, aircraft are separated by 1,000 feet vertically, and the level you get depends on which way you are pointing. Across most of the world an easterly track gets the odd levels — 33,000, 35,000, 37,000 — and a westerly track gets the even ones. Two aircraft on the same airway in opposite directions therefore never share a level.
That is also why the number on your screen is a slightly odd one, and why it holds for an hour and then jumps a thousand feet at a time rather than drifting.
- Separation above 29,000 ft
- 1,000 ft
- Eastbound tracks
- Odd levels
- Westbound tracks
- Even levels
How fast, and why two numbers disagree
Through the air, a modern airliner cruises at Mach 0.78 to 0.85. At cruising altitude that works out near 900 km/h, or about 560 mph, and it barely changes from flight to flight — it is what the wing was designed around.
Over the ground is a different number entirely, because the air itself is moving. A jet stream over the North Atlantic can run at 200 km/h, and it runs west to east. Ride it and you cross the ground at over 1,100 km/h; fly into it and the same aircraft, doing the same airspeed, makes 700. In February 2020 a Boeing 747 crossing the Atlantic in a storm-driven jet stream was clocked at 1,327 km/h over the ground.
This is the whole reason London to New York takes about eight hours and New York to London takes closer to six and a half. Nothing about the aircraft changed.
- Airspeed at cruise
- ~900 km/h
- Ground speed, tailwind
- 1,000–1,200 km/h
- Ground speed, headwind
- 700–800 km/h
What your phone can actually measure
Your phone reads altitude and speed from GPS, which means the speed it shows is ground speed — how fast your position is moving across the map. It has no way to know the wind, so it cannot show you airspeed, and neither can a seatback screen. The number you have always watched on those screens is ground speed too.
Altitude is worth one caveat. Aircraft fly pressure altitude, referenced to a standard setting that every aircraft shares so that everyone agrees on the separation. GPS measures the real geometric height. On a cold day the two can differ by a thousand feet or more, so if your phone reads 36,400 while the crew announce 37,000, both are right and they are answering different questions.
None of it needs a connection. Satellites overhead give the position, the position gives the altitude and the speed, and SkyDot draws all three on a map you downloaded at the gate.
- Altitude source
- GPS, geometric
- Speed shown
- Ground speed
- Works in Airplane Mode
- Yes
Questions
How high do commercial planes fly?
Between 31,000 and 42,000 feet, which is roughly 9.5 to 12.8 kilometres. Long-haul flights usually settle between 35,000 and 40,000 feet. Turboprops on short regional routes stay much lower, around 17,000 to 25,000 feet.
How fast do planes fly?
About Mach 0.78 to 0.85 through the air, which is near 900 km/h or 560 mph at cruising altitude. Speed over the ground is different, because the wind adds or subtracts from it: the same aircraft can cross the ground at 700 km/h into a headwind or over 1,100 km/h with a jet stream behind it.
Why does the same flight take longer one way than the other?
The jet stream. It blows west to east, so an eastbound flight rides it and a westbound flight fights it. London to New York takes roughly eight hours and the return closer to six and a half, on the same aircraft doing the same airspeed.
Can I see the altitude on my phone during a flight?
Yes. GPS gives your phone altitude, ground speed and heading without any connection, so it works in Airplane Mode at cruise. SkyDot shows all three on a map stored on the device.
Why does my phone show a different altitude from the captain?
They measure different things. Aircraft fly pressure altitude against a standard reference that keeps every aircraft agreeing on separation, while GPS measures true geometric height. In cold air the two can differ by a thousand feet or more, and neither one is wrong.
Why is the cruising altitude an odd number like 37,000 feet?
Above 29,000 feet, aircraft are stacked 1,000 feet apart, and the direction of travel decides which levels you may use — eastbound tracks take the odd levels and westbound tracks the even ones across most of the world. It keeps opposing traffic off the same level.