We asked a pilot to explain how high planes fly and why they need to maintain cruising altitude. Here's what he had to say.
How High Do Airplanes Fly—And Why?
Updated on May 30, 2025
If you’re a frequent flier, you may barely pay attention to the routine stages of flight. Still, you know the basics: After takeoff, the airplane climbs for the first 15 to 20 minutes before reaching cruising altitude. At that point, the aircraft levels out and makes its journey at an above-the-clouds height. But just how high do planes fly? And why do they have to stay at a set altitude?
We reached out to Theodore Kyrazis, a JetBlue captain and retired U.S. Air Force F-15 pilot, to find out. Read on for some fascinating airplane facts, including how high planes fly, what happens if they fly too high or too low, and why they stay at a set cruising altitude.
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How high do planes fly?
The cruising altitude of a commercial aircraft depends on the size of the plane. Generally, most commercial passenger jets cruise at an altitude of between 32,000 and 40,000 feet, or 6 to 7 1/2 miles above the ground.
Turboprop planes, which are smaller aircraft that typically carry a handful of passengers rather than hundreds, fly at a lower altitude of about 25,000 to 30,000 feet. Since these propeller planes are often used for short-haul flights, they may stick to lower altitudes simply because by the time they reach a higher altitude, it’s already time to begin their descent.
Don’t worry—your pilot will know exactly how high to fly the plane you’re on. Everything from ideal speeds to maximum altitudes is specified in the Airplane Flight Manual (AFM) for each aircraft.
What happens if an airplane flies too high?
Remember the story of Icarus, the character from Greek mythology who flew too close to the sun and perished when his wings melted? Passenger planes aren’t at risk of melting if they fly too high, but there are cabin-pressure and oxygen concerns that limit how high they can safely fly.
In non-aeronautic speak, here’s what can happen:
- Insufficient emergency oxygen supply: Airlines set altitude limits, Kyrazis says, “to ensure there is enough oxygen supplied to all the masks for the amount of time it takes to accomplish an emergency descent to an altitude where the oxygen masks are no longer required (around 10,000 feet).”
- Sudden cabin depressurization: A loss of cabin pressure can occur if a plane flies too high. If that happens, passengers and crew—including pilots—can lose consciousness. When it happens with a fighter jet, Kyrazis explains, “it’s a simple matter of rolling over and going straight down back to a comfortable altitude in less than a minute. It’s not so simple for a commercial aircraft.”
- Equipment failure: “Almost all modern aircraft have sophisticated computers monitoring aircraft weight, speed, outside air temperature, wind speed and direction, and the angle of the wing relative to the incoming wind,” Kyrazis says. “If a pilot were to try climbing above the recommended altitude and keep going, either the engines would not produce enough thrust to keep climbing or the wings would stall.”
The bottom line? You want your pilot to stick to the recommended altitude!
What are other reasons planes fly at a cruising altitude?
While a lack of emergency oxygen, depressurization in the cabin and equipment failure are all scary outcomes, there are other reasons airplanes cruise at the same altitude for the duration of a flight.
Fuel economy
Commercial airlines need to operate as efficiently as possible to remain profitable. This makes fuel economy one of the most important factors in how high planes fly. The short answer, according to Kyrazis, is that turbojet engines burn less fuel as the air density gets lower. There are some fancy calculations involved, but essentially, the speed and angle of degrees at which the plane climbs are determined both by weather conditions and the size of the plane; bigger aircraft weigh more, in part, because they’re carrying so much heavy fuel, which burns off as they climb.
According to Kyrazis, one hour of climbing may burn off a whopping 10,000 pounds of fuel. And get this: If a major airline saved just 1 gallon of gas on every flight for a full year, it’d save millions of dollars.
The future of air travel may be more fuel-efficient, though. A new type of aircraft called blended-wing body (imagine a wider jet with a, well, blended wing and body) and the International Air Transport Association’s FuellS promise to optimize fuel consumption. And they’ll likely offer an even better flying experience to boot.
Speed
The higher a plane flies, the faster it can travel—up to a point. “Less-dense air at higher altitudes means the actual speed the aircraft is traveling over the ground is much faster than the aircraft speed indicator shows the pilots in the cockpit,” says Kyrazis. That means the plane is making better time than even the instruments show.
But the flip side is that extremely cold temperatures will slow the plane down. To balance that out, pilots find that happy balance between fuel-saving high altitudes and the slowing effects of subzero temperatures.
Turbulence
No one likes to encounter turbulence on a flight, but it’s most likely to occur during ascent and descent. “Much turbulence associated with weather systems can be avoided above 35,000 feet,” says Kyrazis. That is why commercial airliners like to climb above storms and stay there. The exception? Thunderstorms that can reach up to 50,000 feet. When that happens, the airplane has to either go through the storm or around it.
What happens if a plane flies too low?
Despite all the frightening things that can happen if a plane flies too high, flying too low can be just as dangerous. At lower altitudes, aircraft are more likely to encounter poor weather conditions and heavier air traffic, especially from general aviation and smaller commercial or private planes.
Another big risk? Bird strikes. “Most bird strikes occur during takeoff and landing,” says Kyrazis. That includes the 2009 Miracle on the Hudson and the heroic landing by Captain “Sully” Sullenberger. Flying above 10,000 feet significantly reduces the risk of bird collisions.
Why should you care about how high planes fly?
Technically, you don’t have to—that’s your pilot’s job. Still, the cruising altitude of airplanes plays a crucial role in how smooth and comfortable your trip is. Whether your plane is soaring at 31,000 or 42,000 feet, it’s reached that altitude for a reason. Knowing how this affects fuel savings, speed, turbulence and safety can help you appreciate the balance between aircraft performance and operational needs in the sky.
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Sources:
- ICAO: “Airplane Upset Prevention & Recovery Training Aid (Rev 3)”
- Federal Aviation Administration: “Frequently Asked Questions”
- IATA: “IATA Launches FueIIS: Advanced Fuel Efficiency Analytics Solution”
- AIN: “Delta and JetZero Partner on Blended-wing-body Airliners”
- Business Standard: “IATA expects sustainable aviation fuel production to rise in 2024”
