The YB-17 incorporated a number of significant changes from the Model 299, including more powerful Wright R-1820-39 Cyclone engines. Although the prototype was company-owned and never received a military serial (the B-17 designation itself did not appear officially until January 1936, nearly three months after the prototype crashed), the term "XB-17" was applied retroactively to the NX13372's airframe and has entered the lexicon to describe the first Flying Fortress. Ìbéèrè: Bawo ni awọn Air Corps ni anfani lati paṣẹ 13 YB-17s?
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