Boeing KC-97 Stratofreighter was based on the Boeing C-97 Stratofreighter, which was in turn derived from the massive four prop B-29 Stratofortress bomber.  This KC-97L is at Warner Robins Museum of Aviation.  Writes noted historian Mark Morgan, "The KC-97L is 53-0298, ex-NYANG 102nd AREFS/106th AREFG (1969-1972), Suffolk County Airport, Long Island (prior Suffolk County AFB)."  

Adds Mark Pharo: "The Air Force used KC-97s primarily as refueling aircraft but phased them out in favor of the Boeing 707/KC-135, a great plane that still is our primary refueling aircraft today!  The Stratofreighter was flown in civilian versions by Pan-Am amongst others, and I believe that United Airlines had a few with a downstairs piano bar, no joke! 

The KC-97 was grossly underpowered to service most jet aircraft, in particular our primary jet bomber, the B-47 Stratojet. The B-47, in order to refuel from the KC-97, had to dock in a shallow dive with full flaps, otherwise the KC-97 could not maintain a high enough airspeed to refuel it. Two jet engines, one on each outboard wing, were mounted to the KC-97G to give it enough speed to refuel the B-47. The advent of the KC-135 was to accommodate the even faster B-52 which was just coming online as the U.S.’s primary jet bomber. Both awesome planes, incredible advances in technology and they helped lead to the downfall of the Soviet Union. What can you say, so many incredible stories behind them!"