How do planes fly?
The simple answer: lift, thrust, weight, drag. Here’s how these four principles work together to keep a plane in the air.
- A plane’s wing pushes the air downwards while simultaneously being pushed upwards by the air. The forces push on each other and keep the plane flying – this is called the lift.
- Drag is the friction that slows down and opposes the plane’s motion through the air. This happens because there is friction between the air molecules and every part of the plane. With that said, most modern aircrafts are designed to let pass air around it with minimal drag so they fly as efficiently as possible.
- The third element is the weight. The plane has to be balanced in-flight thanks to weight distribution – if the plane’s too heavy on the nose or the tail, it might crash mid-air.
- Finally, we have thrust. Thrust propels the plane forward and is produced by the plane’s propellers or jet engines. In order to cruise through the air swiftly, a plane’s thrust needs to be greater than the drag.
Now that we’ve got that out of the way, let’s discuss the reason why planes fly at high altitudes.
What height do planes fly at?
If all a plane needs to fly is lift, drag, weight, and thrust, why does it have to do that at such outrageous heights? Most commercial and passenger planes spend most of the flight at an average height of 35,000 feet. This is called the cruising altitude – the height at which a plane will plateau after taking off. Different aircraft have their optimal cruising altitude and it’s largely dependent on how much an aircraft weighs.
Above the lowest part of our sky (the troposphere) lies the sweet spot wherein airplanes cruise: the lower stratosphere. There are a handful of factors why aviation scientists have designated this area as the best place to fly a plane – here are some of them:
Air resistance and fuel efficiency
An airplane primarily flies at extreme heights due to air resistance. As mentioned above, drag opposes the thrust that propels the plane forward. This is much more pronounced at lower altitudes where the earth’s atmosphere is thicker. In higher altitudes where the air is thinner and less dense, there’s minimal resistance to the aircraft – thus less thrust is needed to push the plane forward. Subsequently, the aircraft moves in a fast and efficient speed with less fuel burn.
What’s more, when airplanes fly at that height, the air becomes more consistent and stable. Meaning, clouds and weather occurrences (like thunderstorms) are less common.
In case of emergencies
Imagine, you’re in a commercial plane that’s only a kilometre above the ground and the plane begins to act up. Immediately the plane plummets downwards and crashes in 15 seconds. Almost all of the time, plane glitches are easily fixable. And the outrageous heights at which planes fly provides extra time for the pilots and engineers to figure out and repair the problem.
What happens if a plane flies too high?
As previously explained, the higher the altitude, the less dense and thinner the air is. Since lift is generated by the difference in air pressure, there comes a point where the air will be too thin for the aircraft to fly. Additionally, if the plane gets too high, there won’t be enough oxygen to power the engines.
There’s also a risk for passengers to develop hypoxia – this condition happens when there isn’t enough oxygen supply for the body to thrive on. If the cabin pressure suddenly malfunctions and drops, passengers will experience hypoxia – the most common symptoms are: euphoria, visual impairment, severe headaches, drowsiness, and impaired judgement. This is especially terrifying because when left untreated, hypoxia can potentially cause permanent brain damage – all in the span of seconds.
Small planes and helicopters are a different story
According to the National Business Aviation Association, small planes operate on a piston-powered engine. These small machines work like the ones in your car and are engineered to travel shorter distances. Moreover, this type of machinery limits small, private planes from hitting the same altitudes as a passenger aircraft.
In the case of helicopters, these remarkable vehicles fly using rotating blades instead of wings. Along with smaller planes, choppers are also made to only fly short distances. Because of this, they’re unable to attain the height at which aeroplanes fly – maxing out at a little under 10,000 feet.
There’s no need to worry
Even if it’s your millionth plane ride, you could still be a victim of pre-flight jitters. But there’s no need to let it get the best of you. An aeroplane flies between 31,000 to 42,000 feet to give you a safe and smooth experience up in the sky.