I just realized there may be a way ontop of the terminal roof because the only player barries ive seen on the roof is on the sides ( like ontop of the plane and the gas tank) and there may be an elevator to the top not from outside but through the sky lights in the building because alot of them are close to walls. Im not really good at finding glitches but good at possible ideas for them. I also think there isnt a barrier there because i was in a laggy game and my guy jumped up through the ceiling and fell back down again because of the lag.

Again this is only an idea. and yes i know i spelled glitch wrong it was accidental