I have been working on the history of the 421st TFS/FS from WWII onward. I wrote a book on the Night Fighter history, currently working on the Vietnam History, and have been collecting on the F-16s at Hill. (I was a Crew Chief in the 421) Anyway, I have been keeping track of the squadron's serial numbers since they got the F-16, but I am lacking since the year 2000. Would appreciate anyone that might have that information. Please contact me at Blkwidw421@aol.com Jeff.