I hope I convey my point probably, but why do planes go so many thousands of feet in the air? Is it faster that way, or could they achieve similar flight times at a lower altitude?
Does it have something to do with the curvature of the earth?
In: Engineering
It’s much safer to fly over the weather than through it. Theres is much less turbulent air, storms, and lightning at 30,000 feet.
The air gets thinner as you go higher
Less air means less air resistance or drag, so airplanes can both go faster and they use less fuel. So 20,000 > !~~30,000 ft~~ 43,000 ft is a common cruising altitude.
However to travel that high you need to be able to go at a certain minimum speed, and your aircraft has to be pressurized so that passengers can breath.
Modern jet airliners have no problems with this, but smaller propeller driven aircraft often have to fly lower, around 10,000ft otherwise the passengers and crew can’t breath.
Jet fighters and other specialized aircraft are able to go even higher. The SR-71 for example could travel at 85,000ft and well past mach 3.
EDIT: As usids99 pointed out higher altitudes also mean better weather and less turbulence. You are for the most part flying above the clouds.
if you go higher up, you find thinner air, and thinner air causes less drag, and less drag means you can go faster and less power is needed and so it uses less fuel and it’s cheaper
also it’s higher than most weather, so you are gonna have less turbulence, and you can have Jetstreams which are consistent winds that help the aircraft go faster by getting tailwind
The higher up you go, the thinner the air is. That means it’s easier for a plane to push through the air, so it goes faster with less fuel.
Also, if you’re lower, the sound from the jet engines are going to be a lot more disruptive on the ground.
It’s a carefully coreograpphed dance. Thinner air up high means less air resistance. But the engines need air to function. Every airplane has an ideal cruising altitude that’s usually lower than their max capable flying altitude. That’s the planes sweet spot for max fuel efficiency. I’m flying on a gulfstream V as I write this and we’re at 41,000 feet. We could go higher and faster, but this is our sweet spot for fuel efficiency. And that’s what it’s all about, saving fuel
The really high airspace is more controlled, has less traffic, and the higher altitude provides the pilots with more glide distance in the event of engine failure
1. The air is thinner = less air resistance/drag = more fuel efficient = uses less fuel = cheaper
2. You fly above the weather = safer
The less air in front of you, the more fuel efficient it is to go forward.
There is less air at higher atmospheres.
A fun additional problem is that jets use some air for fuel.
Which means at altitudes that are *too high* the jets can neither generate enough air to stay up **or** go forward.
It’s a balancing act:
The faster you go, the more fuel you use, but the more fuel you have.
Likewise: the higher you go the less fuel you need, but the less fuel you have.
It has nothing to do with the curve of the Earth.
The air is thinner, so there is less drag and less noise. That’s better for the speed and fuel economy of the plane, and better for the people on the ground.
Smaller aircraft need to fly at a lower altitude because their cabins aren’t pressurized, so the passengers and pilots wouldn’t get enough oxygen.
Flying at a lower altitude at a lower speed could provide a better fuel economy if the plane was designed for it (due to increased oxygen) but speed is what keeps planes in business.
If you go higher up, the air is less dense. This allows you to go faster and burn less fuel because there is less air resistance.
However, if you go *too* high, the air is too thin for the engines to work efficiently.
Every aircraft has a “sweet spot” combination of speed, altitude, and aircraft configuration that allows it to fly at its most efficient. That sweet spot is where you ideally would like to spend the most time of your flight.
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