01/31/2009. Martin at Omaha, Nebraska, USA, produced this aircraft as a
B-29-55-MO. Subsequently it became a YB-29J when fitted with R-3350-CA-2 fuel injection engines and revised nacelles. Later it was converted to an aerial tanker, designated YKB-29J, to test the Boeing-developed boom aerial refueling system, as seen in this "hook-up" with the F-84G-1-RE. The F-84 was the first fighter with a standard provision for refueling in flight.