Hi, gryphonaire. I’ll quote some comments that I made in this post about a similar question:
. . .as it stands now, track logs should be available (via adding /tracklog to the URL) for 48-72 hours after the last flight for that identification arrived. If you’ve been seeing flights that landed <48 hours ago with missing track data, I’d be interested in hearing about detailed specifics of the incident. Of course, we still save the data indefinitely, it’s just a matter of how far back the map server is willing to look back while it tries to produce a real-time for you.
As it is right now, the best functionality is only reliable for recent flights. As the flight history gets more stale, there’s less work being done to try to present it to the user since it’s considered less relevant. In the near future, we’ll have all sorts of ability to go back in time and by default see all possible, available information.
Also, I should mention that the version of maps available on the production FlightAware site have been deprecated and are no longer in development. We have a new version in pre-release testing internally that will be entirely different and completely amazing by comparison. I wouldn’t spend too much time trying to figure out the idiosyncrasies of the current maps.