We have all gazed up to the sky and seen long contrails from jets way up in the blue and wondered how high they are above us.
These jets are mostly commercial airliners crisscrossing the skies, transporting millions of people around the world. They seem so far away, and they are. They are miles above Earth, but just how far exactly?
I have been an airline pilot for the last 5 years, and flying for 10 years, accumulating over 3500 hours in a variety of aircraft from fast jets to slow, small prop planes. As a pilot many of my family and friends are interested and curious about flying and what happens up front in the cockpit.
One of the most common questions is, “how high can you fly?”
And that’s exactly the question that I’ll answer in depth in the following sections. You will learn how high airplanes fly, why do they need to fly that high, and many other details and some stories from my adventures in the sky.
How High Do Planes Fly?
Commercial planes will typically fly at an altitude between 30,000 and 41,000 feet (9 and 12 km). Short flights on regional aircraft will not go as high because there is not enough time to climb up. The shortest commercial jet flights may only go up to 6,000 feet or just one mile (1.8 km) up in the air.
Frequent travelers have likely heard a captain make one of their mumbled announcements including the cruising altitude. “Folks, welcome aboard flight 989, service to Los Angeles. We are expecting a smooth ride today, we’ll be cruising at 36,000 feet. We’re glad you’re joining us on Travel air.” I do try my best not to mumble my announcements. I’m working hard to break that stereotype one announcement at a time.
You may see and hear small propeller drive aircraft fly overhead. They may be as low as 1,000 feet above you. Helicopters that typically fly below 5,000 feet, and are allowed to go lower most places as they can land on buildings and in tight spaces.
How high a plane is flying is called its altitude. When pilots refer to the altitude they mean how far above sea level an airplane is flying. It is standardized for all aircraft that way everyone is flying according to the same standard and system. Having the same standard system is important especially when airplanes are flying closer together during takeoffs and landings near airports.
Why Do Planes Fly So High?
Most commercial airplanes fly between 30,000 to 41,000 feet. The views from miles in the air are impressive, and it is one of my favorite parts about flying, but there are five main reasons airplanes fly so high: better efficiency, higher speed, to take advantage of high level winds, avoiding weather, and increased range. Let’s see what all of these mean:
Fuel is the largest cost to an airline, accounting for over half of an airline’s expense sheet. Everything in aircraft design and operations is for safety and efficiency.
The biggest difference in flying high is air density. Closer to the earth air is thicker. As altitude increases, there is less and less air. This is also the reason airplanes are pressurized, otherwise, there would not be sufficient air for everyone to breathe.
Airplanes rely on air to create lift over the wings holding the airplane up, but this air also creates drag. Imagine sticking your hand out of the window of your car on the highway. You can feel your hand push up against the air, the faster you drive the higher the resistance.
Thinner air means less resistance so there is less holding you back. For airplanes, this means the engines don’t have to work as hard, saving fuel up higher.
Planes can fly faster at higher altitudes. Also because of the thinner air. At high altitudes, airplanes have to fly faster just to get enough air over the wings to create lift. This is ideal because we want to fly faster anyway, and it creates an efficient operation.
Once again the thinner air provides less resistance allowing the engine to work less to maintain a high speed compared to the thicker air at lower altitudes.
3. Fast High-Level Winds.
The jetstream exists between 5 and 9 miles up. Even if it is a calm day on the surface the winds above can be over 100 miles per hour. This is like a free boost for airplanes.
The fastest wind I have ever encountered was 164mph. Some of my friends have hit 200+mph over the Atlantic Ocean.
Imagine paddling a canoe in a lake versus a fast-moving river. For the same amount of work, the canoe in the river will be moving much faster because it gets to use the stream of the current in addition to the power from the paddle.
This also hurts performance when flying into the wind, however, it is still beneficial to fly at high altitudes despite a strong headwind.
Those big, billowing clouds that turn into thunderstorms are dangerous to fly through and around. Pilots have to maneuver airplanes away from these. They can go up to an altitude of over 45,000 feet. For smaller, propeller aircraft they usually don’t have an option of going above. They must go around the weather which adds time and expense to the flight.
Once at our cruising altitude I spend a lot of time using the onboard weather radar and coordinating with our dispatcher about upcoming weather to make adjustments early to save time and money. The autopilot can do a lot, but it is up to us pilots to make decisions about avoiding weather and turbulence.
This one is pretty straight-forward. If the plane burns less fuel flying higher up, and it flies faster. Then, it will be able to fly a longer distance. A jet would not be able to cross the Atlantic Ocean if it cruised at only 2,000 feet. High altitude flight has enabled the super long flights we are used to today.
So on nearly all accounts, airplanes like to fly high and fast, it is efficient, smoother, and faster.
What is Cruising Altitude?
In that announcement from the captain, they mentioned the cruising altitude would be 36,000 feet. Cruising? Are there different types of altitudes?
Cruising altitude refers to the planned altitude for the primary duration of flight when the aircraft is at its maximum altitude en route to the destination. After an aircraft takes off it begins to accelerate more and climb up all the way to cruise altitude. Usually the cruising altitude of most commercial airplanes is around 35000 feet, but it can vary between 30000 and 41000 feet as we saw earlier.
This altitude has been carefully planned for the flight by airline dispatchers. They use advanced technology that accounts for wind, distance, weather, the specific airplane performance, and traffic to choose the most efficient cruising altitude.
Pilots may elect to change altitudes because of weather, better wind speed, or if it becomes turbulent. Sometimes changing altitude by just one thousand feet can be the difference between bumpy and smooth.
Can Some Jets Fly Even Higher?
We have established that most commercial airliners will fly between 30,000 and 41,000 feet. This is the altitude range I have spent most of my hours. On our cockpit displays I can see all the other airplane traffic and their altitudes. Even when we are flying high at 37,000 feet I will still see jets soaring way above us.
Business jets, like Gulfstreams, Dassault Falcons, and Cessna Citations are capable of flying even higher. They regularly have cruising altitudes of 41,000 to 51,000 feet. They can do this because they carry less weight in passengers, and have longer wingspans.
Flying that high is a major advantage. They are above the congested airspace where all the commercial aircraft air. This means more direct routing, often smoother air above the weather, and even more fuel efficiency. But tThere are challenges associated with flying that high up though.
What Happens if a Plane Flies Too High? Why Can’t an Airplane Just Fly into Space?
You may be wondering if it is efficient to fly so high up, why not just fly all airplanes as high as they can go? As I’m cruising along at 35,000 feet I wish I could just keep climbing all the way up to space, and pretend I’m an astronaut … but the plane can’t do that.
There is a limit for every aircraft’s altitude capability. It is called the aircraft’s service ceiling. It is based on that airplane’s performance, the weather, and how heavy it is loaded.
On long flights, it is common for an aircraft to start at a lower altitude, and then climb as it burns off fuel, becoming lighter. This is called a step-climb.
The limiting factor for how high airplanes fly is the thin air high up. At very high altitudes there simply is not enough air to sustain lift, and an aircraft would stall, meaning it no longer can produce enough lift to hold the airplane up. This is a dangerous situation to get into, and requires us to be extremely vigilant when flying at high altitudes.
Rockets launch into space by burning a ridiculous amount of fuel and can escape the atmosphere, but airplanes will always be limited by air. The wings need lift and as altitude increases air eventually decreases to nothing.
Because the air is so thin, high up oxygen becomes more important. If a rapid depressurization were to occur there is so little oxygen at high altitudes that without immediately putting on an oxygen mask, we would pass out.
Above 40,000 feet you see in the following table how important it is to immediately have the ability to receive oxygen. We are trained for this procedure. We have special masks in the cockpit that can be donned in under three seconds, and we practice this every year in the simulators.
|Altitude||Time of Useful Consciousness|
|45,000 feet MSL||9 to 15 seconds|
|40,000 feet MSL||15 to 20 seconds|
|35,000 feet MSL||30 to 60 seconds|
|30,000 feet MSL||1 to 2 minutes|
|28,000 feet MSL||2.5 to 3 minutes|
|25,000 feet MSL||3 to 5 minutes|
|22,000 feet MSL||5 to 10 minutes|
|20,000 feet MSL||30 minutes or more|
It is so important that above 41,000 feet one pilot is always required to have their oxygen mask on. In addition, anytime my other pilot leaves the cockpit for a bathroom break I must put on my oxygen mask until they return.
A well-known accident in aviation history involved the professional golfer Payne Stewart. They were flying a Learjet at an altitude of 45,000 feet. The airplane lost pressurization and for some reason, no one was able to get to oxygen. According to the chart, they would have had only 9 seconds or less if it was an explosive decompression.
F-16’s intercepted the jet since it was unresponsive and the F-16 pilots noted the windows were fogged up with condensation indicating a rapid depressurization. Everyone onboard was incapacitated, and a few hours later the airplane ran out of gas and crashed into South Dakota…
What is the Highest-flying Plane in History?
Ever since man figured out flying, there has been a competition for who can fly the highest and the fastest. Disregarding flight that is rocket-powered or launched from another airplane, like the X-15 rocket plane, the highest operating aircraft was the SR-71 Blackbird reaching 85,000 feet.
The SR-71 was a long-range, high-speed reconnaissance aircraft. It could cruise at 85,000 feet at speeds over Mach 3.0. This allowed it to use its high-powered cameras to spy on enemy targets while being too high and too fast to be shot down.
While it is reported that the maximum altitude is 85,000 feet there is a lot of secrecy surrounding this aircraft, and some sources say it can climb to over 100,000 feet!
At those altitudes, the pilots need to wear astronaut-like suits because the atmosphere is so hostile and thin their blood would boil without protection. They can see the curvature of the earth!
The SR-71 had its last flight in 1999. Since then the highest-flying plane is another reconnaissance jet. The U-2. It is capable of altitudes around 70,000 feet. Despite being designed in 1955, there are still 30 of these aircraft operational.
The need for high flying aircraft became less as satellite technology increased. High powered cameras on satellites have largely taken the role that aircraft during the Cold War used to provide.
Popular Planes Maximum Cruising Altitudes
|Airplane||Maximum Cruising Altitude|
|SR-71 Blackbird||85,000 feet|
|Lockheed U-2||70,000 feet|
|Gulfstream G650||51,000 feet|
|F-16 Falcon||50,000 feet|
|Cessna Citation Longitude||45,000 feet|
|Boeing 747-8F||43,000 feet|
|Airbus A350||43,000 feet|
|Airbus A380||42,000 feet|
|Boeing 737-800||41,000 feet|
|Airbus A320||39,000 feet|
|King Air 350||35,000 feet|
|Cirrus SR22T||25,000 feet|
|Cessna 172||14,000 feet|
These are maximum altitudes for these jets. These numbers can be replicated only when certain weather conditions and aircraft performance parameters are met.
For most jets it is not uncommon to go to the service ceiling, however, it is more likely to cruise a few thousand feet below this. It is difficult to get an airplane to climb up to their absolute limits. It is usually more advisable and safer to cruise below the maximum altitude.
How to Find an Aircraft’s Altitude?
There are a couple of ways to see the altitude of aircraft. A website called FlightRadar24 tracks airplanes all over the world. If you see an airplane flying overhead, you can open the app, see your location, and see the airplane displayed above you. If you select it you will get information on its route, the type of plane, its speed, and altitude.
Flightaware also has flight information. Before a flight, you can see the filed flight plan and cruising altitude for any commercial flight.
Airlines that have seatback entertainment often have a flight tracker display. It will list the aircraft’s speed, altitude, and some other fun facts about the flight.
Another option is coming up front and asking the pilots before or after the flight. We, as pilots, are always happy to share some of our passion for flying. None of this information is secret, sometimes I have people ask if it is classified. It is all public information and we are happy to tell you!
Take note the next time you hop on a plane. Have a listen to the announcement, or look at a flight tracker. You can see how high you are flying and enjoy seeing cars looking like tiny little dots below you knowing that every part of the flight has been carefully crafted to ensure safety and efficiency.