Continuity mistake: When Bourne is talking to Firsch, the gun he is holding changes from a Glock in the shots facing Bourne, to a SigPro when the shots face Firsch.
Continuity mistake: When Landy is looking at Jason's file it says his blood type is A+. When Jason looks at his old dog tags it says his blood type is O-.
Continuity mistake: Noah Vosen's face goes from completely clean shaven (very smooth and shining skin) to very short stubble and back again when explaining the secret project to Pamela Landy in his office.
Continuity mistake: The conversation Bourne has with Landy at the end of The Bourne Supremacy is repeated in this film, about an hour and fifteen minutes in - the conversation is absolutely word-for-word identical, so clearly it's the same one. However, in Supremacy, it is a bright, sunny day, but in Ultimatum, the weather is overcast with snow on the ground. Landy's phone rings in Supremacy, but vibrates in Ultimatum. Finally, the other agent doesn't enter her office during the phone call in Supremacy.
Continuity mistake: In the chase scene involving Bourne and Desh, when Bourne comes to a stop on the rooftop, his jacket is zipped. In the next shot his jacket is open. In the next shot his jacket is zipped, as he begins to run again.
Continuity mistake: When Bourne is fighting with Desh in the bathroom scene, the wash basin gets broken off the wall.But in the next camera angle it is back in place again.
Continuity mistake: When Desh is chasing Nikki and Bourne is chasing Desh, in a shot of Bourne from overhead, he is wearing black converse type tennis shoes (black with white rubber on the toes). As the chase continues, Bourne's shoes are shown several times to be solid black.
Continuity mistake: When Pamela Landy is looking at Jason Bourne's induction paperwork, the date of his induction is 06-01-1999. However, the date of his first assassination (Neski) is 1998. The assassination of Kyriacou is also listed as having taken place in 1998. Both dates are obviously before he had completed the Treadstone induction. (01:11:55 - 01:13:25)
Continuity mistake: When Nicky is first seen in the movie, with Bourne pointing a gun at her, her hair changes between shots.
Continuity mistake: During the fight scene between Bourne and Desh in the bathroom, Bourne's watch keeps disappearing and reappearing on his left arm.
Continuity mistake: At the end of the movie, in the flashback when Bourne recalls his training process several years ago, Hirsch looks younger, but Bourne looks just like the present date, with an edgy and thin face, opposite to the round-childish face that he had then (which we are reminded of during all the movie via photos in his portfolio).
Continuity mistake: During the shooting in the parking garage, it's a Chrysler that rounds the corner, but as it approaches Bourne, he shoots at a Ford Crown Victoria.
Continuity mistake: When Desh goes to meet Nicki, he parks his scooter. Walking behind him(from left to right) is a guy wearing a black shirt with orange stripes. The camera then switches to Bourne and then back to Desh. The man in the shirt is now seen walking towards Desh(from the left) but is still at least 40 feet away from him. (00:53:40)
Continuity mistake: In Madrid Bourne calls the emergency line and says he's in 334 Norte street, which triggers cops to show up. When Bourne arrived at the building he looked at the door and it was a 2 digit number which one can faintly see it starts with a 1. (The filming location took place at number 10 Virgen de los Peligros street).
Answer: Knowing Bourne, he must have had a keycard on his person. Remember that Landy guided Bourne back to the CIA New York Headquarters; she could have easily slipped a keycard in the Taxi Cab when Bourne was being picked up at the airport. All he would have to do then is avoid being detected by using the fire exits (hence going through the back).
Jason Riley