Note: Some of the pilots who were in the real Flying Tigers were reportedly so embarressed by the movie when they were invited to the premiere that they were caught trying to sneak out of the theater...also, John Wayne reportedly got drunk with some pilots while on a tour in New Guinea and they left him out on the tarmac on a cot, stark naked. He woke up with a hangover, rolled over and went back to sleep (from The Internet Movie Databases's Flying Tigers page).
"Remember Pearl Harbor" came out in mid-'42.
Now I'm not saying that it, or United 93, was not also "too soon."
But what bothers me is the failure, in most MSM discussions of whether "United 93" is "too soon," to mention the elephant in the room, namely Michael Moore and his "Fahrenheit 9/11."