If the ship was not there, one of the objectives didn't complete. And to push characters, like the Pres, you gotta make him look to one side, then to another, and so on. The fast way of doing this (check any Statue vid on GE, at the Valentin part) is using C-right and C-left, and moving backwards. Or you can use opposite strafes.
Whatever, someone can explain that better.