Continuity mistake: When Ripley is driving the APC, the passenger side front tire is on fire and engulfed in flames. When she runs over the alien with the same tire, the flames are completely gone. In the next shot and several shots after, the tire is completely engulfed in flames again.
Continuity mistake: In the beginning, Ripley wakes up in a sweat, practically crying. She rings Burke on the visual phone and she has a droplet of sweat on her nostril, but it's there, then it isn't, then it, is; it comes and goes.
Continuity mistake: When Ripley pulls Newt out of the cocoon, she has cocoon stuff all over her back, but a second later it's gone.
Continuity mistake: In the beginning, when they find the colonists, they have IDs under their skins, but on the read-out there's only about 6 of them, when there should be about 100 of them. Later, on the read-out, we see the right amount of IDs.
Continuity mistake: As the ship carrying the marines to the planet where communication has been down for too long, the pilot of the ship says, "Where's the damn beacon? Oh, I see it." But when she says the last bit, there is no vision of the beacon; it only comes into sight a few seconds later.
Chosen answer: The studio was considering a sequel before Cameron was involved, but regarding directing it, Ridley Scott told "The Hollywood" in a 2008 interview, "They didn't ask me! To this day I have no idea why. It hurt my feelings, really, because I thought we did quite a good job on the first one." The studio liked Cameron's script and at that time he had enough clout to be able to insist on directing it.
raywest
It would have been a gamble to choose Ridley Scott as he had no experience with action films, James Cameron had proved himself with films such as Terminator.