Registration deactivated for aircraft:
Here's couple of pages from the pdf's
There's one I could find again that had a lot of registered numbers being deactivated. Gonna keep looking for it, anons there's a lot of unknow aircraft out there. It pretty much bagan when Obama was elected in '09, some before mostly under him.
https://ia800408.us.archive.org/12/items/394337-n675pl-3-pdf/394337-n675pl-3-pdf.pdf
https://ia600406.us.archive.org/3/items/394297-n374ax-3-pdf/394297-n374ax-3-pdf.pdf
https://ia801000.us.archive.org/10/items/394295-n20321-3-pdf/394295-n20321-3-pdf.pdf