Submitted by Angela

The alien ship the Earth shot down at the beginning of the movie was not the original race of aliens, but another alien race coming to warn Earth of a 2nd impending attack and to offer to evacuate humanity to a refugee planet.

Humans rescue the friendly alien and use a decoy version of it to lure the queen alien of the new invasion fleet out of her ship and kill her. The friendly alien promises to teach Earth its advanced technology so they can lead the other planets targeted for invasion an intergalactic war against the invasive alien species.