As a more generic follow-up to crhptic, what resources are available to travelers to track down specific information about past flights? For instance, are flight manifests eventually made available to the public for decades-old flights, and if so, who would have them (specific airline, governmental agency, etc.)? Would an airline be able (or willing) to track down past flight information if you were not a frequent flyer member at the time of the flight? Is there any library that has a historical airline timetable collection? Does OAG sell old comprehensive timetables (e.g., from the 80's)? Do acquiring airlines (e.g., AA and TWA) have historical information at their disposal of the acquired airline?

I know I've asked a lot of questions, but I would like to know what options I have to fill in some holes in my past travels. I'm guessing I'm SOL, but I wanted to ask the experts before I give up.