(Spoilers ahead, though in fairness the movie is 42 years old)
Pretty late in the movie Alien (1979), it's revealed that Weyland Yutani Corporation knew of the existence of the Xenomorphs, and in fact deliberately sent the Nostromo to their location to retrieve them. It is also revealed that Ash a) was aware of the mission and charged with facilitating the creature's delivery; and b) was an android, and therefore not in particular danger from the Xenomorph.
What I don't quite understand is, if WY was deliberately sending a ship to retrieve it, and was planning to put an android on said ship to safely transport it back, why use humans at all? It seems like it would have been significantly safer and easier from WY's standpoint to send a ship with all androids who were aware of the mission. That way not only are people not unnecessarily put in harm's way and killed, but also, because the mission doesn't need to be run clandestinely, there is much less of a risk of crew who are unaware of the mission harming the specimen (which is obviously what ends up happening). Is there any reason I'm overlooking that would explain this decision, or is it just a flaw in the screenplay?