airplanes cruising altitude when flying over mountains


I recently took several flights across the Andes mountains and the flights seemed to be close to the mountains at cruising altitude and were mostly turbulent. I read somewhere that the optimal cruising altitude for a jet is about 35k feet… does this altitude need to be adjusted when flying over high mountain ranges? Do the mountains cause additional turbulence?

In: Engineering

I’m no expert but I don’t think they adjust their altitude. Even Mount Everest only reaches about 29000 feet above sea level, well under your normal cruising altitude. I’d also bet that flight paths are set to avoid mountain ranges as much as possible too

So I’m not a commercial pilot, but a private pilot. Mountains come with eddies, also known as mechanical turbulence. Basically, as the air passes over and around the mountains, it is disrupted and so causes swirling action that can affect planes.

I don’t believe that altitude changes much over high mountain ranges, as cruising altitudes are actually set by a standardized law, but I’m pretty sure they’re avoided if possible. There’s no reason to subject the pilot and the passengers to additional stress.

35,000 is over a mile higher than Everest (29,029 ft). No adjustment required.

Actually, this may not be entirely true. Flight levels are based on direction. Flights north and south are on different levels as are east/west flights in order to prevent mid-air collisions.

Cruising altitude is a balance between two effects – as you go higher, 1) the air gets thinner, which means less drag as you move through it, but 2) thinner air means less oxygen, which makes combustion engines less efficient. If you’re flying over a mountain, neither of these things really changes because the density of the air depends on gravity, and the mountain underneath the plane doesn’t change that. (If you’ve ever been high up, like climbing a mountain or in cities like Denver or Mexico City, you can feel the thinner air as you breathe.)