Coffin corner (aerodynamics)

Coffin corner is when an airplane is flying so high and so fast that it's really hard for the pilots to keep control of it. Like when you're on a skateboard going really fast down a hill and it's hard to stop or turn because you're going so fast.

When the airplane is up really high, the air is much thinner than it is closer to the ground. The faster the airplane goes, the more it pushes the air down and creates pressure that helps it stay up. But up really high, if the airplane goes too fast, the air can't go around the plane fast enough and starts to get all mixed up. This makes it hard for the airplane to be stable and it can tip over and crash.

The coffin corner is where the airplane is going so fast that it's right between the point where the air pressure can't help it stay up anymore and the point where the air is too mixed up for the airplane to control itself. It's called the coffin corner because it's like flying in a really dangerous coffin, and if the pilots make any mistake or the airplane has any problems, it could crash really easily.

So, in conclusion, coffin corner is a really dangerous situation for airplanes where they're going so fast and so high that it's hard for the pilots to keep control, like when you're going too fast on a skateboard down a hill, and it's called coffin corner because it's like flying in a really dangerous coffin that could crash at any moment.