I would assume that Soyuz capsules aren't considered aircraft. They don't really fly, per se, they get launched on a rocket and then fall like a rock back to earth.

You could make a stronger argument for the Space Shuttle, which re-enters at about Mach 25, IIRC, and is gliding. But it's not doing so under power.

> Soyuz capsules aren't considered aircraft

While I suspect you're right, Soyuz capsules do use aerodynamic lift to control descent rate and steer to the landing site. In some ways they are very, very (very) inefficient gliders.

I'd expect the definition of a powered aircraft to include the ability to maintain some given flight altitude and speed for some appreciable amount of time.

It is possible to do something sort of like this in a space capsule returning to Earth, where you muck up your entry vector and come in at too shallow an angle. You can then (depending on the circumstances) bounce off the atmosphere, and gain altitude briefly. And then you probably come back in the atmosphere on too steep an angle, and die due to g-load or overheating.

Yes, but they're outside the atmosphere and therefore don't have a Mach number.

A Soyuz capsule that never enters the atmosphere would have a very upset crew.

Soyuz can be manually piloted, but are normally automated (Progress can not be piloted and is essentially the same thing after all). They're also not aircrafts.