Though GTA V has a number of UFOs littered around Los Santos, you can't really get a close look at most of them. Which means it's easy to miss the fact that the UFOs sometimes do have things inside of them.
GTAForums member xHaviiHx recently shared images of the UFO at Fort Zancudo, pictured above, and it's actually pretty neat to see all the details. Turns out, the aircraft does have pilots! You might already know that if you've taken a look at the 3D models, but no-clipping on PC allows us to see that the pilots actually have uniforms and everything. The ship also has all sorts of circuitry running through it:
Cool, huh? Previously, players have found that it's possible to go inside other ships, which is how we know what's inside, say, the sunken UFO wreckage:
You can watch CosmoEpoch no-clip inside three different UFOs in this video clip below -- it has more angles than the images I've provided.
You'll note that none of the non-story GTA UFOs seem to have as much detail to them as the Fort Zancudo one. But maybe that's just because people haven't figured out how to get the game to load more of the UFOs yet... /tinfoil hat