Nicolas Cage was the first actor to be given the script. Producers Michael Shamberg and Stacey Sher circulated the Andrea Berloff's screenplay over to Creative Artists Agency, where it was given to Oliver Stone and Cage.
The scene outside the port authority building has a shadow of AA flight 11 moving over the officer from his right to left, which he followed visually, indicating a northerly flight path at that time of day as the sun would have been in the southeast sky. Flight 11 was headed south and at that time, its path was never between the sun and the port authority terminal, and it struck the north side of the North Tower.
On the scene where the fire truck is driving down Broadway, the Engine Company number is listed as "99"; although the FDNY's highest "90s" engines only go to "97", this is not a goof - Engine 99 is featured in the FX network television show Rescue Me, and is making a cameo appearance here; 9/11 was a frequent theme throughout that series.
Mother in Hospital: My son works the elevator in the south tower... he's a good boy. Then I saw that building going down like a pancake... damn thing is I yelled at him. I made dinner and he got held up at work... food went to waste. Now all I wanna do is hold him.
The first song in the movie trailer is "Piano Theme" from the World Trade Center Original Soundtrack.The second song heard is the theme song from "The Life of David Gale".