Not so fast!
From the source (http://greyfalcon.us/pictures/Flying%20Saucers.htm):
All of these photos are computer generated forensic composite illustrations. None of them are official USAF photos. Since the USAF seems very reluctant to de-classify these birds, these illustrations were created to give people an idea of what they looked like. Yes, they really did exist, but due to some stability problems, this particular model was scrapped.
Pull!