I’m working on some project to compare historical availabilities of seats between city pairs in Europe, too bad their historical api doesnt return aircraft type (so number of seats its unknown). I also couldn’t find how far back their data goes.
... for my project, I actually got some historical paper schedules of the official aviation guide, basically they’re phone books. I hope to find a decent/affordable database for more recent data. (MIT students/alumns actually get access to a database going back to 1979, but alas no access for outsiders...)
The Official Aviation Guide became OAG who will have what you need in digital form but at steep commercial rates, as will their competitor Innovata (Cirium)
The actual seats bit is surprisingly complex if you want accurate figures, as the same aircraft type can have wildly different numbers of seats depending on layout and class configuration. OAG/Innovata's standard schedule product has the aircraft variant normally assigned to a route shown, and they survey the airlines on the seating configurations of their aircraft calculate capacity and ASKS. I believe Cirium now cross reference this with flight tracking data to get data based on the actual aircraft used (which solves edge cases like substitutions or an airline operating aircraft with differently configured A330-200s on different routes) - doing that was part of the masterplan when I worked for them before they acquired Flightstats.
... for my project, I actually got some historical paper schedules of the official aviation guide, basically they’re phone books. I hope to find a decent/affordable database for more recent data. (MIT students/alumns actually get access to a database going back to 1979, but alas no access for outsiders...)