In Through the Looking Glass (Season 3) we learnt that the Others were constructing a Runway, whose purpose was unknown. Here's the dialogue between Sawyer and Juliet:


SAWYER: So, when you pulled us out of those polar bear cages and put us on the chain gang, what the hell you have us breaking all those rocks for anyway?
JULIET: We were building a runway.
SAWYER: Runway, for what?
JULIET: [Turns to him] The aliens.
[She smirks]
JULIET: I don't know what for, do you think they told me everything?


http://www.youtube.com/watch?v=IZACfxJmumI

Did the Others already know that the Oceanic Six had to come back to the Island (perhaps by plane)? Did the Losties inform them in one of their time travels?