Go to the area with the airplane. Jump on its wings to reach the lower level. Drop 
from the plane, then go to the left of the furthest wing (towards the front of the 
plane). Once you reach the rock wall, find the slightly hidden hole. Go through it,
and follow the path along the cliff side to reach a cave with a giant typewriter 
and get the "Creative Space" achievement. After Alan is done speaking, go on top 
of the typewriter to read a paper that reveals more of the storyline.