Duba wurin da ke ƙasa sannan ka amsa tambayar daga baya a cikin harshe ɗaya kamar yadda wurin yake:  Passage: Ko ta yaya, aikin USAAC ya burge shi da aikin samfurin, kuma a ranar 17 ga Janairu, 1936, ta hanyar doka, Rundunar Sojan Sama ta umarci 13 YB-17s (wanda aka sanya Y1B-17 bayan Nuwamba 1936 don nuna kudaden F-1 na musamman) don gwajin sabis. YB-17 ya haɗa da wasu canje-canje masu mahimmanci daga Model 299, ciki har da injin Wright R-1820-39 Cyclone mafi ƙarfi. Ko da yake da samfurori da aka kamfanin-mallakar da kuma taba samu wani soja serial (da B-17 lakabi kanta ba ya bayyana a hukumance har sai Janairu 1936, kusan watanni uku bayan da samfurori ya fadi), da kalmar "XB-17" da aka yi amfani da baya ga NX13372 ta airframe da kuma ya shiga lexicon don bayyana na farko Flying sansanin soja mai ƙarfi.  Tambaya: Ta yaya rundunar sojin sama ta iya yin odar jiragen YB-17 guda 13?
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