Conventional Alien Craft

I just figured out something. (Yes, whilst shitting.) All of the traditional "UFOS" have typically been a flying saucer with a dome window on the top, but why not a shapeless vehicle because in space there is no top or bottom. It's because the craft is modified (either by a hoaxer's mind or the aliens themselves) to the Earth's gravity! (Which could debunk any "gravity-law-breakeing" theories because any conventional alien craft would have to have a propulsion system.)
We also modify OUR aero-vehicles as such, note the rocket and the airplane. But even something that goes into space has been modified to fit gravity because it started out in gravity. Problem: once it reaches space, it's still modified. The only example that I can think of that doesn't fit this model is the satellite.
Hypothesis: A vehicle that is travelling through space that does not conform to gravity by shape or propulsion was either A)Built in space. B)Modified in space C)Built on planet and sent to space, then released, or D)Teleported into space.
Thought: But what of the alien craft that is not conventional such as the "cigar-UFO" or the Triangle of lights UFO...?

That was an original thought asshole, I didn't get sources. I don't need 'em. I studied Ufology when I was younger. But let me ask you when I say UFO, or "alien space craft" what do you think of? In fact, the first American sightings were of "foo" or fire in the sky (basically gioant fireballs) and then came the flying saucer twice by a pilot and once by a man in Michigan. Then, the sightings (and hoaxes) took off.