Different types of aircraft fly at different heights and largely depends on whether they are pressurized, the type of engines they have and their role (leisure, business, commercial or military).
Commercial aircraft today fly at altitudes up to 42,000 feet (which is just under 8 miles high). Concorde used to fly at altitudes up to 60,000 feet (over 11 miles high) and at that height you could see the curvature of the Earth. Some military aircraft (the SR-71 Blackbird) could fly up to 85,000 feet.
This article will show how high do planes fly for various groups of aircraft.
How high do commercial planes fly?
Modern commercial airliners normally fly between 30,000 feet and 42,000 feet, with an average of around 36,000 feet. The maximum altitude has increased over the years as engines have developed to become more powerful which allows them to fly at higher altitudes.
Concorde had a very high operating altitude of 60,000 feet. This was mainly possible due to its very powerful Rolls Royce Olympus engines. At such a high altitude the air was thinner so there was less drag which enabled it to fly faster at more than twice the speed of sound (1341 mph).
In the days of commercial aircraft with piston engines, back in the late 1940s and the 1950s, aircraft couldn’t fly as high as today as piston engines were less high powered and would not work efficiently at altitudes of 30,000 and above. For example, two of the most common long range commercial aircraft back then, the Lockheed Constellation and the Douglas DC6, generally operated at around 24,000 feet.
Some piston engine bombers were able to fly at almost jet airliner altitudes. For example, the B-17 Flying Fortress could fly at just over 35,000 feet but this wasn’t for reasons of fuel efficiency but instead as it made them safer from fighter aircraft and ground based guns.
How high do private jets fly?
Private business jets often fly higher than commercial jets as they generally have a higher power to weight ratio which allows them to cruise at higher altitudes.
The Gulfstream G650 for example can fly up to 51,000 feet.
How high do fighter jets fly?
Fighter jets can fly at quite high altitudes, often around 50,000 feet. This is due to them normally being aerodynamically very efficient and to having powerful jet engines which give them a high power to weight ratio.
Fighter jets are built to perform different roles such as ground attack, air to air combat or even multi-role, so their operating altitude may vary depending upon their role.
The highest flying military aircraft
The military aircraft that flew the highest (and the fastest) was the Lockheed SR-71 Blackbird which was developed in the 1960s as a reconnaissance aircraft for the USAF.
It could fly at altitudes of over 85,000 feet and at speeds in excess of 2200 mph, which is greater than three times the speed of sound (Mach 3).
How high do light aircraft fly?
Most light aircraft fly between 2,000 feet and 6,000 feet although they would often be capable of climbing higher to altitudes of 14,000-15,000 feet. For example, the popular Cessna 172 has a maximum ceiling (altitude) of 13,5000 feet.
Light aircraft are limited as far as the altitude they can fly because:
- They are not pressurized
Light aircraft are normally not pressurized, so unless the aircraft was fitted with an oxygen system, pilots might suffer from lack of oxygen if flying above 15,000 feet.
- Under-powered engines
Most light aircraft’s engines are generally not very powerful so have a limited maximum ceiling height
- They make short flights
Mostly light aircraft are used to travel relatively locally so even if they could, climbing to a high altitude would not make sense
- Air traffic control restrictions
Light aircraft can be restricted to flying at lower altitudes by airspace regulations and also by the competence/licensing of the pilot. Many private pilots are not trained to fly on instruments alone so need to fly within good view of the ground (under VFR – Visual Flight Rules).
Why do planes fly so high?
There are a number of reasons why aircraft fly high, rather than at lower altitudes. These include:
- Less air resistance
The higher an aircraft flies the less dense the air becomes. The lower the air density, the less resistance (known as drag) there is on the airframe of the aircraft so the faster it can fly.
- Fuel efficiency
At higher altitudes, due to the lower air density, the less fuel the engines need to propel the aircraft along at a certain speed. In addition, the temperature at high altitudes is lower, and generally, the lower the temperature the more efficiently a jet engine runs.
- Above the weather
Flying at altitudes of up to 42,000 feet means that the aircraft are normally flying above the weather systems where the air is more stable so the flight will be more comfortable for passengers.
How do pilots decide what height to fly at?
The gross weight of the aircraft (including the empty aircraft, crew, passengers, baggage, cargo and fuel) will largely determine the best cruising altitude for the aircraft to fly at. However, after that, a few other factors come into play.
Air traffic control (ATC) will ultimately have the final say in what altitude an aircraft will fly at. A pilot may request ATC to give them a different altitude, perhaps to avoid a weather front or just to fly more efficiently, but it is up them if that request is granted, based in traffic congestion etc.
In much of the world, particularly in busy airspace, aircraft fly along airways. Airways are basically the invisible highways in the air which make up the air traffic control network.
In a road network ,which is basically two dimensional, one lane (or lanes) travel on one direction and another lane (or lanes) travel in the opposite direction, next to each other.
In an airway, which is in three dimensions, lanes are stacked one on top of another, with odd numbered altitudes (eg 31,000, 33,000, 35,000 feet etc) traveling in one direction and even numbered altitudes (eg 30,000, 32,000, 34,000 feet etc) traveling the opposite way.
An air traffic controller will allocate which altitude an aircraft will fly at (either odd number or even number of thousands of fee) based on its direction of travel along the airway..
How high is space?
As aircraft fly higher and higher it may be interesting to know whether they are reaching altitudes that might be considered being in space. But they have a long way to go yet.
How high is space depends on which organization is defining it. The US generally define it as starting at an altitude of 264,000 feet (50 miles) but internationally it is normally regarded as starting at 380,000 feet (62 miles) which is also known as the Kármán line.
So even the highest flying military aircraft are still a long way from being in space.