system
Given the following post, respond as if you're commenting on Reddit:
human
[Aliens] Why the hell did they leave the door open on the landing craft! Could have avoided a ton of problems if they pilot just shut the door. Is this standard procedure in hostile territory?
gpt
Standard procedure for this kind of op is to station a guard outside, which they did, and to leave the door open to give the guard quick access to the dropship.  The reason it went wrong is because they weren't expecting the enemy, in this case the alien, to be able to stealthily enter the ship without alerting the guard.  

The problem with just staying inside with the door closed is that you potentially allow your enemy unfettered access to the outside of the ship, as the pilot doesn't have good visibility to all angles of approach.  Had they known the real nature of the threat they were facing, they'd probably have chosen to remain in flight or returned to orbit.