They do qualify that to make the list they must be retired from regular passenger service, regardless of other status.
First on the list is the venerable Boeing 707.
A classic airliner by any measure...but also still a military necessity and lifeline for ongoing wartime operations.
Sadly this old workhorse is still on the front lines in the guise of ISR platforms (RC-135 variants, and E-8 JSTARS) as well as the KC-135, an aerial tanker that the Air Force has been trying to replace for close to a decade.
Unfortunately, as Congressmen posture and postulate, these 'classics' get older and older. The US cannot fight a war without them....
Take a look at this old photo from around the early 1960s. Both the B-52 and KC-135 are still major workhorses in the USAF 40+ years later. 40 years. Classic my ass....