You may wonder how high planes fly and why they fly at that particular altitude. Most often, commercial airplanes fly anywhere between 30, and 42, feet in the air, which equals five to seven miles high. The main reason is fuel efficiency. Put simply, airplanes use less fuel in higher altitudes where the air is thinner, increasing the efficiency and saving them money at the same time. In fact, a lower altitude can put too much strain on the engine and cause it to run at a higher speed than what it is able to handle.
This means a less-efficient engine that costs money and puts a strain on the entire plane. Higher altitudes mean less thrust for the plane because the air is thinner yet a high compression ratio and thermal efficiency can be maintained. The plane gets a much higher true air speed TAS than it would at a lower level because planes are always able to fly faster once the engine is burning less fuel.
To put that in perspective, the peak of Mount Everest measures at 29, feet. The area is called the lower stratosphere, which is just above the troposphere, lowest part of the atmosphere, according to the UCAR Center for Science Education. Flying in this area has many benefits that make flying one of the leading ways for travelers to get from one place to another.
The biggest reason for this altitude lies with fuel efficiency. The thin air creates less drag on the aircraft, which means the plane can use less fuel in order to maintain speed. Less wind resistance, more power, less effort, so to speak.
Spending less on fuel is also great for airlines, for obvious reasons. So, flying too high can also cause problems. Plus, the higher a plane goes, the more fuel it has to burn in order to get there so there are some drawbacks with certain altitudes as well. Flying higher means planes can avoid birds usually , drones, and light aircraft and helicopters, which fly at lower altitudes.
The troposphere — that is the atmospheric layer closest to the ground — is home to most of the world's weather phenomenons. Usually measured up to 36, feet, this is where clouds are most likely, as well as heavy rains and high winds.
Aircraft prefer life in the stratosphere, which means less turbulence. Flying so high also means that aircraft are able to avoid other airborne traffic, such as light aircraft or helicopters, which fly lower, as well as insects and birds.
Light aircraft do not have pressurised cabins, therefore stick below 10, feet. Any higher and the pilot is required to don an oxygen mask to keep conscious.
Should something bad happen to an aircraft at 35, feet, like losing power in its engines, the pilot has much longer to deal with the situation, than if the aircraft was just at 10, feet. This may sound silly, but remember that planes can still land safely even if both engines fail — so having more time to get your ducks in a row before attempting such a manoeuvre could save lives.
See also: The truth about oxygen masks on planes. The higher you get, the colder it gets, up until 40, feet. If the temperature at ground level was 20C, at 40, feet it would be C.
At 35, feet the air temperature is about C. Has anyone seen comedian Eddie Izzard's Glorious , where he does a sketch about taking a flight in a very small aircraft with only a handful of passengers? He jokes that the pilot's announcement is thus: "Welcome to Flight One from here to there. We'll be flying at a height of ten feet, going up to 12 and a half feet if we see anything big.
Aircraft must not fly less than feet above the "highest fixed object" beneath them and pilots must make sure that they are high enough to clear the congested area below in the event of engine failure. Obviously, these don't apply to take-off and landing when aircraft are in controlled flight paths. See also: The world's 10 scariest airports to fly into. There is no maximum altitude for flying, however, engines will struggle as the oxygen levels fall, and communication with the ground will become a greater challenge.
The record altitude for a jet plane is , feet, set by Alexandr Fedotov in flying a military Soviet MiGM.
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