The voice message came first. It's always been there, and isn't particularly helpful. My best guess is it's leftover from a parallel timeline. We've run into a lot of those here.
The airplane is something Eliot rigged up to actually help new arrivals.
As for the natural flow of development and technology? We're in some sort of a time loop. People appear here randomly but also disappear. When they disappear, they don't remember being here and it's like they were never gone at all.