Visible crew/equipment: Near the beginning of the film while Clarice is being interviewed, we can see a black T-shape during a shot of the floor. This is shown to be an actor's mark, as someone steps right into it a few shots later. (00:12:58)
Revealing mistake: During the scene in which Krendler shows the fake Lecter postcard, look closely and you can read the line: "Sounds like him to me" although this line is part of Krendler's speech, and not part of the message itself. Forgetting your lines, Mr. Liotta? (01:21:55)
Answer: As seen in the first film and in this one, Lecter demonstrates an almost supernatural ability for eluding the law and seemingly being in two places at once. This film was made in the year 2000, before airport security became extremely tight in late 2001. At that time (before 9/11), it was still possible to enter an airport's main concourse through the baggage claim or even from the tarmac without passing through rigorous security. As ingenious as Lecter was, he could have accessed the airport in a number of ways back then. Relieving another passenger of his boarding pass and identification would be no problem for Lecter, either (simply leave the passenger's body in an airport toilet and assume his identity). For the most part, it was Lecter's calm, self-confident charm that allowed him to slither through society always ten steps ahead of the law.
Charles Austin Miller