During the main mission for the Brotherhood of Steel, the mission "Spoils of War" has a glitch in it where you cannot jump from the Vertibird and onto the roof. Due to this glitch that means 2/4 of the factions in the game cannot be completed. The other being the Railroad due to the Boston after Dark glitch.

Edit: after mashing every button on my controller it worked. Still glitched though, a lot of people are having the same problem. It took me about 5-6 attempts to get the quest to work