That's great- thanks for the link Microwave. I was able to fill in the blanks on a few registrations back to the '90s I didn't quite get!
Do you know of an equivalent site where one could find listings for flights operating to the US, from the US to international, or simply within other countries such as Canada, Europe etc.? The USDOT site seems to only provide registrations for flights departing and arriving within the US.