Interesting.My only problem is that no single aircraft is in fact "Air Force one" that term is the call sign given to the particular aircraft that the President of the United States is flying on. They actually have several VC-25s(special 747) that are capable of serving as "Air Force One".I find the claim that a DC-9 (C-9A to the USAF) "may have been Air Force 2" very doubtful to be honest.They where used as transports for generals and most served as medical transports.The other problem with the claim is that their is never an "Air Force Two" call sign and no "Air Force Two" to be a part of.The nearest thing to this would be the back aircraft that is available and the E-4B that typically flies into the same region that Air Force One is present in when ever it is overseas the E-4B you could say is a flying Pentagon.
George W. Bush actually was the last president to fly on a 707 though from Regan on down the VC-25 was the preferred air frame.According to Wikipedia anyway.
Some one has a scrap DC-9 and is trying their hardest to get as much cash out of it as possible.
Here is a photo of the DC-9 it carriers the markings of a VIP aircraft the DC-9s it has department of state markings basically a diplomat plane.who ever is selling is being very liberal and boosting its status.
http://www.flickr.com/photos/chrisk48/7397741932/
Its real history
http://www.airport-data.com/aircraft/N681AL.html