Threat of an alien invasion...a bluff?
One thing that crossed my mind several times in this film was the fact that Wyatt mentions a few times that killing the alien would bring about mass devastation...an invasion possibly...but would that be the case?
IMHO - NO
From what we see there is likely to be only 1 ufo of indeterminate size and 1 alien...though I think an early comment refers to another alien and there is the scene where Wyatt is somehow "invisible" to those aliens going by in the clearing
The alien IS a tough son of a bitch but seems to die at the end - yes it did take a LOT of explosives but nothing the military could not whip out quickly. Plus the alien seemed a bit hurt by the shaving foam when it got sprayed(?)
Why does the UFO clear off after the blast IF they are going to wreak havok?
IMHO the alien plants a seed of terror in Wyatt to protect itself, an idea that if it is killed BIG trouble will start.