Basically, its gonna take them aliens hundreds of years to travel through space (thats travelling at the speed of light - However if they can warp space it may only take a few hours, but thats as good as impossible) so we are not going to see a UFO with live aliens in it, if we see a UFO
at all
.
I know a while agao they found continuous wave patterns coming from space, which they though could possibly be an alien transmission, but it actually turned out to be a double neutron star.
Basically, if an alien UFO landed on earth, we would know about it. We are not blind. If it really did have aliens in it, the aliens would do a bit more than hover a few inches above the ground, they would want to make contact with us.
The nearest we have got to contacting an
intelligent
alien lifeform is the space probe
Voyager
.
-Suit