Editing Boeing B-17 Flying Fortress (section)

=== Initial orders ===
[[File:B17F - Woman workers at the Douglas Aircraft Company plant, Long Beach, Calif.jpg|thumb|Installation of fixtures and assemblies on a tail fuselage section of a B-17 at the [[Douglas Aircraft Company|Douglas]] plant in [[Long Beach, California]], October 1942]]

Despite the crash, the USAAC had been impressed by the prototype's performance, and on {{Nowrap|17 January}} 1936, through a legal loophole,<ref name="Erickson"/><ref name="Meilinger" /> the Air Corps ordered 13 YB-17s (designated Y1B-17 after November 1936 to denote its special F-1 funding) for service testing.<ref name="Zamzow.34" /> 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),<ref name="Bowers1976.p12" /> the term "XB-17" was retroactively applied to the ''NX13372's'' airframe and has entered the lexicon to describe the first Flying Fortress.

Between 1 March and 4 August 1937, 12 of the 13 Y1B-17s were delivered to the 2nd Bombardment Group at Langley Field in Virginia for operational development and flight tests.<ref name="Swan Mil p75" /> One suggestion adopted was the use of a [[pre-flight checklist|preflight checklist]] to avoid accidents such as that which befell the Model 299.<ref name="Meilinger" /><ref name="Checks2" />{{NoteTag|The idea of a pilot's checklist spread to other crew members, other air corps aircraft types, and eventually throughout the aviation world. ''Life'' published the lengthy B-17 checklist in its 24 August 1942 issue.<ref>[https://books.google.com/books?id=fk4EAAAAMBAJ&pg=PA65 "B-17 checklist"]. ''Life'', 24 August 1942.</ref>}} In one of their first missions, three B-17s, directed by lead navigator [[Lieutenant]] [[Curtis LeMay]], were sent by General Andrews to [[Interception of the Rex|"intercept" and photograph the Italian ocean liner ''Rex'']] {{convert|610|mi|km}} off the Atlantic coast.<ref name="Zamzow.47" /> The mission was successful and widely publicized.<ref name="Maurer" /><ref name="USAF Rex" /> The 13th Y1B-17 was delivered to the Material Division at Wright Field, Ohio, to be used for flight testing.<ref name="Y1B-17" />

A 14th Y1B-17 (''37-369''), originally constructed for ground testing of the airframe's strength, was upgraded by Boeing with exhaust-driven General Electric [[turbo-supercharger]]s, and designated Y1B-17A. Designed by [[Sanford Alexander Moss|Sanford Moss]], engine exhaust gases turned the turbine's steel-alloy blades, forcing high-pressure air into the Wright Cyclone GR-1820-39 engine supercharger.<ref>{{cite web |url = https://aviationshoppe.com/manuals/wwii_aircraft_superchargers/wwii_aircraft_turbosupercharger.html |title = World War II – General Electric Turbosupercharges |website = aviationshoppe.com |access-date = 8 June 2017 |archive-date = 8 October 2019 |archive-url = https://web.archive.org/web/20191008054906/https://aviationshoppe.com/manuals/wwii_aircraft_superchargers/wwii_aircraft_turbosupercharger.html |url-status = usurped }}</ref> Scheduled to fly in 1937, it encountered problems with the turbochargers, and its first flight was delayed until {{Nowrap|29 April}} 1938.<ref name="Donald" /> The aircraft was delivered to the Army on {{Nowrap|31 January}} 1939.<ref name="Bowers Boeing p293-4" /> Once service testing was complete, the Y1B-17s and Y1B-17A were redesignated B-17 and B-17A, respectively, to signify the change to operational status.<ref name="Wixley p23" />  The Y1B-17A had a maximum speed of {{cvt|311|mph|kn kph}}, at its best operational altitude, compared to {{cvt|239|mph|kn kph}} for the Y1B-17. Also, the Y1B-17A's new service ceiling was more than {{convert|2|miles|m}} higher at {{convert|38000|ft|m}}, compared to the Y1B-17's {{convert|27800|ft|m}}. These turbo-superchargers were incorporated into the B-17B.<ref>{{cite book |last1=Caidin |first1=Martin |title=Flying Forts: The B-17 in World War II |date=1968 |publisher=Bantam Books |location=New York |isbn=9780553287806 |pages=80, 95–99}}</ref>

Opposition to the Air Corps' ambitions for the acquisition of more B-17s faded, and in late 1937, 10 more aircraft designated B-17B were ordered to equip two bombardment groups, one on each U.S. coast.<ref name="B-17B" /> Improved with larger flaps and rudder and a well-framed, 10 panel [[Acrylic glass|plexiglass]] nose, the B-17Bs were delivered in five small batches between July 1939 and March 1940. In July 1940, an order for 512 B-17s was issued,<ref name="Pop1" /> but at the time of the [[attack on Pearl Harbor]], fewer than 200 were in service with the army.<ref name="Meilinger" />

A total of 155 B-17s of all variants were delivered between {{nowrap|11 January}} 1937 and {{nowrap|30 November}} 1941, but production quickly accelerated, with the B-17 once holding the record for the highest production rate for any large aircraft.<ref name="Serling.p55" />{{NoteTag|Quote: "At the peak of production, Boeing was rolling out as many as 363 B-17s a month, averaging between 14 and 16 Forts a day, the most incredible production rate for large aircraft in aviation history."<ref>Serling, p. 55</ref> This production rate was, however, surpassed by that of the [[Consolidated B-24 Liberator]]: at its peak in 1944, the [[Willow Run]] plant alone produced one B-24 per hour and 650 B-24s per month.<ref name="Willowrun">Nolan, Jenny. [http://info.detnews.com/redesign/history/story/historytemplate.cfm?id=73&category=locations "Michigan History: Willow Run and the Arsenal of Democracy."] {{webarchive |url=https://archive.today/20121204140927/http://info.detnews.com/redesign/history/story/historytemplate.cfm?id=73&category=locations |date=4 December 2012 }} ''The Detroit News'', 28 January 1997. Retrieved: 7 August 2010.</ref><!--end NoteTag-->}} The aircraft went on to serve in every World War&nbsp;II combat zone, and by the time production ended in May 1945, 12,731 B-17s had been built by Boeing, [[Douglas Aircraft Company|Douglas]], and [[Vega Aircraft Corporation|Vega]] (a subsidiary of [[Lockheed Corporation|Lockheed]]).<ref name="Yenne.p6" /><ref>Herman, Arthur. ''Freedom's Forge: How American Business Produced Victory in World War II'', pp. 292–99, 305, Random House, New York, 2012. {{ISBN|978-1-4000-6964-4}}.</ref><ref>Parker 2013, pp. 35, 40–48, 59, 74.</ref><ref>Borth 1945, pp. 70–71, 83, 92, 256, 268–69.</ref>
{{blockquote|Though the crash of the prototype 299 in 1935 had almost wiped out Boeing, now it was seen as a boon. Instead of building models based on experimental engineering, Boeing had been hard at work developing their bomber and now had versions ready for production far better than would have been possible otherwise. One of the most significant weapons of World War II would be ready, but only by a hair.|Jeff Ethell, 1985<ref name="Pop1" />}}