I was at work in knoxville, tn looking thru windows at sky facing south when i saw a silver disc come zooming by heading from ne to sw almost directly towards mcgee-tyson airport which is class b airspace at est. 350 mph and 3000-3500ft. a few minutes later saw an air liner descending from s to n on downwind leg of landing pattern for the airport at one third the speed of object. i am ex navy having served aboard helicopter carrier and do have a private pilot's license