Pilot explains why planes can't fly higher than 40,000ft despite Concorde reaching as high as 60,000ft

Most commercial aircraft cruise between 35,000 and 40,000 feet, which is interesting when we remember that Concorde actually flew at around 60,000.

As always, the reasons are both technical and financial.

And the altitude chosen is generally a result of both.

But there’s something worth pointing out.

Most aircraft cruise between 35,000 and 40,000 feet for a reason

Most commercial aircraft today cruise at altitudes between 35,000 feet (around 10.5 kilometers) and 40,000 feet (around 12 kilometers) for several key reasons.

The first thing worth noting is that this isn’t a hard cap: they could fly lower as well as higher.

While thinner air would reduce drag and improve fuel efficiency, flying higher would involve diminishing returns for a bunch of reasons.

First, jet engines lose power at higher altitudes because the air is too thin for efficient combustion, and this leads to a related second problem: lift.

Wings generate lift through air flow, and air is thinner above 40,000 feet.

Also, the system that keeps the cabin at a comfortable, breathable pressure faces significant stress the higher the plane climbs.

In other words, 40,000 feet isn’t a hard physical wall; it’s just the sweet spot.

Why Concorde could fly higher

Nothing about Concorde was ‘normal.’

The cockpit was mad, with dials and switches on the walls, and it required a three-person crew.

Its speed was also obviously far from common.

With that in mind, the fact that Concorde generally flew at a much higher altitude shouldn’t surprise us.

At supersonic speeds, air density creates increased drag, which can be reduced by flying higher, where air is thinner.

The engines that Concorde used were optimized for higher speeds and higher altitudes, precisely for that reason.

Also, the plane’s speed could turn the engines (and therefore the plane) into a furnace, which is something else that can be mitigated by flying higher, where air is much colder.

Last but not least: by flying well above the majority of earth’s atmosphere, Concorde avoided most weather-related turbulence, making the ride more comfortable.