When Mac receives the message from Carmichael he states that Carmichael has been dead for 30 years. That would make Mac well over 50 years old and Carmichael would have been killed during WWII . Also, when he speaks to Walt Harmon, Walt says Carmichael was grabbed in eastern Europe in 1964. That would be only 10 years earlier not 30.
The final shootout is an homage to the final shootout and chase in Bullitt (1968), but between that show's filming and this one, metal detectors and security guards were installed at all passenger gates. The killer gets through them to shoot an intelligence agent and flees onto the airport runway. (Another character pulls a gun in the baggage claim area, but that's not covered by airport security.) Later, Mac runs down a jetway to chase the killer, and his gun DOES set off the security alarm. Two airport policeman tackle him -- and he shakes them off.