Questions about Alien, Aliens, Prometheus and Alien: Covenant

FMaldo

I have some questions for staff and community.

In Alien 1979 the planet where Ripley's crew descended (where one of them was attacked by one of the creatures out of the egg) had space suits because they could not breathe on the surface of that plane.

In James Cameron's 1986 Aliens, the men who accompanied Ripley to the same planet did not wear space suits because they could already breathe in the open air.

In Ridley Scott's Prometheus of 2014, the crew of that ship needed space suits to be able to walk on the same planet.

Why in the movie of 1979 could not breathe?
Why in the 1986 film if you could breathe?
Why in the movie of 2014 could not breathe?
What is the explanation?
Alien crew: Covenant descends on the planet where Alien starts in 1979 or on the planet where the engineers live, where were Elizabeth Shaw and David after Prometheus?

Thank you.

Batchpool

In 1979, LV426 was not terraformed. In 1986 it had been terraformed by Weyland Yutani to give breathable atmosphere. Prometheus is set on LV223, not LV426. As for the planet Covenant is set on, it is not established if this is LV 426 or not. Only watching Covenant will reveal the real identity of this planet.

Hope this helps clear things up.

Hemlock

What Batchpool said.

FMaldo

Many thanks Batchpool and Hemlock.