The second production B-17F-1 was converted into the first YB-40 Prototype. The development of the Lockheed – Vega built XB-YB-40 ,was the Army Air Forces attempt to bring additional defensive firepower to the bomber formations flying against the German Luftwaffe fighters.The X in XB was used for” EXPERIMENTAL” and the Y in YB signified ” SERVICE TEST “.They were rushed into combat in May, 1943 with the 92ndBG at ALCONBURY.
Potez 75 1953 The Potez 75 was a French light ground attack pusher configuration monoplane of the 1950s. It was modified to light ground attack configuration and tested in the Algerian War, excelling in this role and orders were placed for 15 pre-production and 100 production machines in 1956. This order was cancelled the following year as part of defence budget cuts.