[deadbeeves]

>Sorry for the pedantry, but if they are flying around in the earth's atmosphere then they are not "spaceships" even if they are being operated by extraterrestrials.

I'll see your pedantry and raise you my own pedantry. The fact that a hypothetical craft flies around in an atmosphere does not imply that it's not a spaceship. A vessel could conceivably be capable of flying through some fluid at one time and through the vacuum of space at another, and would thus be called a spaceship. For example, the Space Shuttle was a spaceship even when it was operating under aerodynamic forces. Since we're talking about alien ships, they would have to be alien spaceships, because otherwise we would have to accept that these aliens have the necessary infrastructure and facilities to land their spaceships somewhere (some kind of alien spaceport on Earth?), disembark, and board their alien aircraft to fly around Earth's atmosphere, which is an even more ridiculous idea.