1. is the Master database of aircraft details (Most of which is automatically updated)
2. is a database of photos by Registration / Tail Number
Clearify on the database structure:
First we have airframe table (database), which record manufacturer,model, c/n, year, etc. This table is indexed on a unique number.
Then comes the aircraft table, which record registry number, airworthy info, etc as well as linking them to an airframe. This table is indexed on the registry numbers.
As an airframe can bear multiple registry numbers over time, it's possible there're multiple records in aircraft table linking to the same airframe. This behaviour can be observed from the aircraft profile pages in "Also Registered As" line. Example here: http://www.airport-data.com/aircraft/TC-JMD.html.
Also a registry number can be used on multiple airframes over time, so it's possible to have multip records with same registry in the aircraft table. This behaviour is shown as "x aircraft records found." in the left side of aircraft profile page. Example here: http://www.airport-data.com/aircraft/N2029Z.html
Aircraft photos are stored in a separate table, with links to aircraft table. If the aircraft for a photo does not exist in aircraft table, then the photo can only be found by search or browse through photographer's gallery.
Ken