The first of the "Big Ass" B-17's arrived England to equip the US 8th Air Force in July 1942. All the planes had been modified with enlarged gun windows and 0.50-calibre guns on either side of the nose. Further modifications were made to them after they were operational including work on the radio, bomb rack, lighting, oxygen, extinguisher and survival systems. By the time the B-17E had been shipped across the Atlantic, newer models were already coming off the Boeing production line. In fact, the B-17E was only on full combat status for just over two weeks before the appearance of the B-17F's
The B-17E was not used in great numbers for combat because the F model was so different in performance that it made joint operations, using both planes unlikely. The B-17E took a back seat and was eventually esed as a trainer, a transport and a target-tower. With its armaments removed it could give better handling and speed.