I was on a flight looking down at the cars on the highway and it hit me, like the higher you go the higher the radius is to cover the same distance as ground transportation. I’m sure there’s a cool reason and history. To make up for the extra fuel to get up that high and the extra miles added. Anyone? Does it have to do with less air pressure. And the efficiency aerodynamic wise? Or noise pollution? Visual pollution? I just always took it as a non ask, “We’re this high, cuz we’re in a plane. Duh”
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It’s alot more fuel efficient because air resistance is lower at higher altitude, and import consideration when your travelling several hundred miles an hour.
Airplanes fly at approximately 10000 meters, so the increase in circumference is 0.15% as compared to ground level. In other words, a 1000km trip on the ground (in a straight line, which is even less likely on the ground) is a 1001.5km trip by aircraft.
The reason aircraft fly at higher altitudes has to do with the engine and wing efficiency, as well as weather avoidance and exploiting phenomena like the jetstream.
It gets very technical if you want the details and that’s not really ELI5 material.
The amount that planes fly does not significantly change based on their altitude. The circumference of the Earth is about ~40,000km. The earth has a ~6370km radius. At a typical altitude of 40,000 feet (or 12km), you get up to ~40,100km in circumference. That’s a 0.25% increase.
The reason for their chosen altitude is ultimately money, but the reason for that is better fuel economy for the trip. This is a combination of higher speeds and lower drag from the lower air density at altitude. This is balanced against the amount of fuel spent on maintaining altitude versus fuel spent on maintaining speed.
Air density drops significantly the higher you go. Less dense air means less resistance to moving, which means it’s easier to travel.
30000 ft is only 10 km, which is only 0.16% larger than the Earth’s radius. But air pressure (and density) is lower by ~75%, making it a lot easier to fly.
Additionally, the higher you fly, the less likely you are to bother residents with the super loud engines of the plane. It also gives you more room to avoid obstacles or other planes (shorter flights or smaller planes tend to fly lower).
One of the central reasons behind aircraft altitude is that, as the air gets thinner with every foot climbed, planes can travel more easily and therefore move faster and burn less fuel, saving money. The air resistance is less the higher you are.
I’m also sure there are safety reasons and probably this also allows a higher amount of traffic in the same area… Like planes being right on top of each other at different altitudes etc
I don’t know all the reasons, but I can say it’s partly for traffic control. At least in Canada, there’s standardizations that depending whether you’re flying west or east, you fly at odds or evens numbers of thousands of feet (don’t remember which is which). Because smaller planes often don’t have pressurized cabins and emergency systems to fly up higher in the atmosphere, those heights are used by larger planes.
Air resistance mostly. Going that fast creates a ton of drag, so you want to minimize the amount of air there is around you. They also avoid a lot of unwanted weather by flying that high and minimize noise.
And it doesn’t really take that much extra fuel to get higher up, since you’re also saving fuel on the descent.
It’s more efficient and takes *less* fuel, because the air resistance is lower since there’s less air. That’s absolutely the most important reason, but there are some other benefits.
One is that it gives a large amount of wiggle room for “lanes”. There are well-established routes between airports. By giving a high ceiling, planes have plenty of room to go lower to avoid other planes. To be clear, they’re not getting anywhere near each other anyway, but the margins for safety in commercial flights are very large.
Going so high also puts them above the vast majority of bad weather. Tall storm clouds can get high enough to interfere with commercial flights, but *most* storms don’t really get that high. Wind at that height tend to be dominated by big, slow weather fronts and predictable jet streams, so there *usually* isn’t much turbulence and wind shear is rare.
It’s good for safety in the event of a loss of power. All planes can glide without power to the engines, but commercial planes are big and heavy so their glide slope is not great. The higher up they are, the more time they have to look for and get to a safe place to land. Every flight plan – commercial or otherwise – includes information about airports along the route and which among them can safely accommodate an emergency landing of a plane of its size and weight, so pilots always know where they can go. But they still need to get the plane there, and without power height = distance.
Plane has big engine and wings to take off. Once cruising, most of the power and wing is useless weight. At that point, you better climb to less dense air so the extra wing and engine will drag you less while a little power and a little lift from wings will keep you up.
Distance wise, climbing 6km while traveling 3000 is not a big difference in distance or fuel consumption. But you consume 50% less fuel for 3000km due to less air drag.
There are edge cases when the flight is so short that the plane won’t benefit much from the climb and will climb less.
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