Editing Boeing B-17 Flying Fortress (section)

=== Initial USAAF operations over Europe ===
[[File:Marks and letters on the tails of B-17 during WWII in Europe.jpg|thumb|Marks and letters on the tails of B-17 during WWII in Europe]]

The air corps – renamed [[United States Army Air Forces]] (USAAF) on 20 June 1941 – used the B-17 and other bombers to bomb from high altitudes with the aid of the then-secret [[Norden bombsight]], known as the "Blue Ox",<ref>{{cite news |url=https://www.nps.gov/articles/second-generation-norden-bombsight-vault.htm |title=Second-Generation Norden Bombsight Vault |work=[[National Park Service]] |access-date=2 July 2017}}</ref><ref>"Blue Ox." ''National Geographic Magazine'', Vol. LXXXIII, Number One, January 1943, p. 7, Ad(i).</ref> which was an optical electromechanical gyrostabilized [[analog computer]].<ref>Peterson, Paul. ''Ludington Daily News'', 16 April 1994, p. 1.</ref> The device was able to determine, from variables put in by the bombardier, the point at which the bombs should be released to hit the target. The bombardier essentially took over flight control of the aircraft during the bomb run, maintaining a level altitude during the final moments before release.<ref name="Baugher B-17B" />

The USAAF began building up its air forces in Europe using B-17Es soon after entering the war. The first [[Eighth Air Force]] units arrived in [[High Wycombe, England]], on {{Nowrap|12 May}} 1942, to form the 97th Bomb Group.<ref name="Northstar" /> On {{Nowrap|17 August}} 1942, 12 B-17Es of the 97th, with the lead aircraft piloted by Major [[Paul Tibbets]] and carrying [[Brigadier General]] [[Ira Eaker]] as an observer, were close escorted by four squadrons of RAF [[Supermarine Spitfire|Spitfire IXs]] (and a further five squadrons of Spitfire Vs to cover the withdrawal) on the first USAAF heavy bomber raid over Europe, against the large railroad [[Classification yard|marshalling yards]] at [[Rouen]]-Sotteville in France, while a further six aircraft flew a diversionary raid along the French coast.<ref name="WoF p59-0" /><ref name="AAF combat" /> The operation, carried out in good visibility, was a success, with only minor damage to one aircraft, unrelated to enemy action, and half the bombs landing in the target area.<ref>{{citation |chapter-url=http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-18.html |chapter=Chapter 18: Rouen-Sotteville, No. 1, 17 August 1942 |volume=I: Plans & Early Operations, January 1939 to August 1942 |pages=662–63 |date=1975 |orig-date=1948 |first=Arthur B. |last=Ferguson |editor-last1=Craven |editor-first1=W F |editor-last2=Cate |editor-first2= J L |title= [[The Army Air Forces in World War II]] |via=Hyperwar Foundation}}</ref>

Two additional groups arrived in Britain at the same time, bringing with them the first B-17Fs, which served as the primary AAF heavy bomber fighting the Germans until September 1943. As the raids of the American bombing campaign grew in numbers and frequency, German interception efforts grew in strength (such as during the attempted bombing of Kiel on 13 June 1943<ref name="Bowman.7" />), such that unescorted bombing missions came to be discouraged.<ref name="Weigley 339" />