So in late 2004, Ben had Kate and Sawyer helping the Others clearing the runway. It must have been fairly well known among the rest of the Others what the purpose of the activity was, because Juliet told them later that it was "a runway" (before joking that it was for the aliens). But the Others have never been seen with any aircraft.
It's only four years later, in 2008, that the runway finally gets used, when Ajira 316 makes its landing.
So are you wondering also: Why did the Others put a runway there? Almost as if someone knew that it would be needed at that exact spot, waiting for Ajira 316?
I found the answer on Lostpedia: probably the definitive Wiki devoted to Lost.
According to the Official Lost Podcast for March 19th, 2009, it was none other than Jacob who ordered the runway to be built.
That both makes perfect sense and begs even more questions about Jacob. Hope we'll get to find out more about him soon, 'cuz he's the most captivating mystery that this show has.