The American Airlines DC-3 "Flagship Skysleeper" airplane that lands in "Fort Worth" is shown pulling away from the gate for departure. However, in subsequent shots, two different aircraft are used. In the long shot of it turning around at the end of the runway, it's not even a silver DC-3, and in the takeoff shot, it's a different AA DC-3 (note the missing "Flagship Skysleeper" emblem).
The Saint looks up Martin Eastman's address in a directory. Eastman's entry precedes that of someone called Earle, which of course it should follow in alphabetical order.
As the plane is taking off from "Fort Worth" a cart is being wheeled back into the terminal building; the film's negative was flipped because "American Airlines" on the cart is written backwards.
The airport at "Fort Worth" as indicated in this film, does not have towering hills as shown in the background. In reality, it's basically flat terrain as far as the eye can see.