Slow moving huge saucer shaped craft flying over. an Air Force Base.

UFO?  I was a B52 crew member.  The year was 1965.  My Buddy & I were on nuclear alert for our twice a month week-long stay in the alert facility at the end of the runway at Bergstrom AFB, Austin, Texas.  We were standing on the patio waiting for it to be time to watch the nightly movie.
(Sidebar, my Buddy was the retired USAF person who accompanied the 2 police officers that got Whitman up on the University of Texas Tower mass shooting event.)  All of a sudden a shape started going from South West to the North East.  It was saucer shaped with lighted porthole type windows.  It was so huge and going so slowly that I wondered how it could sustain flight.  We looked at each other and shrugged our shoulders.
We dared not say anything to each other much less the higher-ups because, if nothing else, we could lose our Top Secret clearance and hence our jobs.
Date of sighting is approximate.  PD