Immortalized in such movies as Memphis Belle, the Boeing B-17 Flying Fortress was without a doubt the war's most famous and glamorous bomber. With elegant and clean lines, the B-17 packed a powerful punch of twelve or more .50-in machine guns and could carry a massive bomb load over enemy territory making it the epitome of the strategic bomber concept which had been extensively advocated by such pre-war figures like Billy Mitchell. B-17 daylight raids over Europe with the 8th Air Force began in 1942 and were stepped up the following year as part of the Combined Bomber Offensive although some 1943 raids, like those against Schweinfurt and Regensburg, proved disastrous since B-17s were vulnerable without fighter escort despite their defensive firepower. With the introduction of long-range P-47s and especially P-51s in 1944, B-17s began the systematic destruction of German cities and industry which eventually led to the collapse of the Luftwaffe although the effect on the final Allied victory has been hotly debated since. The UK was the only other wartime user but post-war operators included Bolivia, Brazil, Chile, Denmark, Dominican Republic, France, Israel, the Netherlands and Portugal although some were retained in the US for use as airliners and as aerial tankers to fight forest fires. Ultimately, the B-17 would also be the first in a line of successful "Fortress" bombers built by Boeing which would continue flying up to this day.

The B-17 was designed as a 1934 requirement for a high-flying heavily armed bomber and the prototype Model 299 was first flown on 28 July 1935. Initial production variants included the B-17B and C which were first used by the RAF to no success due to heavy losses. The slightly improved B-17D was used in the Philippines but were quickly wiped out the Japanese assault in 1941 yet along with the B-17C it perfomed the bulk of early war missions by the USAAF. The upgraded B-17E and F were the first variants used extensively by the USAAF in Europe and were successful until a defensive blind spot in the nose was found and exploited by the Luftwaffe, this resulted in the B-17G with twin chin-mounted guns. The B-17G was the definitive and most produced variant of the Flying Fortress and the only other notable wartime variant was the YB-40 escort with as many as 30 machine-guns. Lastly, a testament to the versatility of this aircraft is the plethora of roles (mostly post-war) in which it served with considerable less fanfare, among these executive transport, radar early warning, SAR, and target drone. Small numbers of B-17s served with RAF Bomber and Coastal Commands. These corresponded to USAAF versions as the Fortress Mk. I (B-17C), Mk. IIA (B-17E), Mk. II (B-17F) and Mk. III (B-17G).