Under the terms of the Lend-Lease law, which was passed on March 11, 1941, the War Department was empowered to sell, lend or lease war material to "the government of any country whose defense the President deems vital for the defense of the United States".
Almost immediately, the Royal Air Force (RAF) requested the delivery of a number of B-17s. Although the USAAC was chronically short of B-17s itself, the service reluctantly agreed to divert twenty aircraft out of the order for 38 new B-17Cs and deliver them to England. The twenty B-17C Fortresses allocated to Britain under Lend-Lease were taken off the B-17C production line at Boeing. These aircraft were essentially similar to USAAC B-17Cs, but they had all but the single nose gun replaced by 0.5-inch Browning machine guns, and self-sealing fuel tanks were installed at Wright Field before the Fortress Is were flown to Britain. They were known as Model 299T by the manufacturer, and as Fortress I by the RAF. RAF serials AN-518 through AN-537 were assigned to these planes, although they were initially painted with the incorrect series letters AM rather than AN.
Although the Army did not consider the B-17C as being combat ready (the E-version was already under procurement as the result of combat reports from Europe), the RAF was sufficiently desperate that these planes were immediately pressed into front-line service.
The Fortress I was to be used by No. 90 Squadron, based at West Raynham. Things got off to a bad start right from the beginning. On its delivery flight to Britain, the first Fortress I ran off the runway when landing at West Raynham, wiping off its undercarriage. It was fated never to fly again, sitting forlornly by the side of the runway, slowly being scavenged for spare parts.
The RAF planned to use the Fortress I on unescorted daylight bombing raids against targets in Europe, relying on the vaunted defensive firepower of the Fortress to fend off fighter attacks. The first sortie with Fortress Is was flown from Polebrook on July 8, 1941 against Wilhelmshaven. Three planes took part. Engine trouble forced one of the planes to divert to a second target, but the other two went on to attack the naval barracks at Wilhelmshaven from an altitude of 30,000 feet. Unfortunately, the planes were not able to hit anything from such extreme altitudes. In addition, their crews found that the temperatures at this altitude were so cold that their defensive machine guns froze up when they tried to fire them. However, all planes returned safely to base.
On July 24, a group of Fortresses attacked the French naval installation at Brest. They were equipped with the Sperry rather than the famous Norden bombsight. The Fortresses attacked from 30,000 feet and managed to miss their target completely. German fighters pounced on the formation, but all bombers returned to England. However, one of the raiding Fortresses was so badly shot up by the German fighters that it disintegrated upon landing.
A third Fortress I was lost in an accidental fire on the ground.
An operational sortie was made by three Fortresses against Oslo, Norway, but all three planes were destroyed by Luftwaffe fighters. One of the Fortresses apparently fell more or less intact into enemy hands, probably giving the Germans their first look at the American bombsight.
A seventh Fortress was lost during a high-altitude test flight. This plane was testing equipment at high altitude when something went wrong.
An eighth Fortress suddenly appeared in a vertical dive from out of a cloud and went straight into the ground. It was never determined what went wrong.
By September of 1941, RAF Fortresses had flown 22 attacks against targets such as Bremen, Brest, Emden, Kiel, Oslo, and Rotterdam. A total of 39 planes had been dispatched, out of which eighteen planes had aborted and two had been forced to bomb secondary targets because of mechanical problems. Eight Fortresses had been destroyed in combat or lost in accidents. Discouraged by these losses, the RAF decided to abandon daylight bombing raids over Europe.
Four Fortress Is were later sent to the Middle East, where, until May 1942, they undertook night attacks against enemy positions at Benghazi and Tobruk. In February to April of 1942, 5 of the remaining Fortress Is in Europe were transferred to RAF Coastal Command. No 220 Squadron operated two of them on convoy escort duties in advance of the arrival of the new Fortress IIA. No. 206 Squadron used Fortress Is briefly for crew training in advance of receiving its first Fortress IIAs. No 59 Squadron is recorded as having one Fortress I for the same purposes.
Two surviving Fortress Is found their way to India in May of 1942, and were taken over by the USAAF late that September..
On the balance, the combat debut of the Fortress was a resounding failure. The Fortress Is encountered numerous mechanical failures during flight, their guns had an annoying tendency to freeze up at high altitudes, and their defensive armament was completely inadequate to fend off determined enemy fighter attacks. In addition, it was found that it was much more difficult than expected to hit anything when trying to bomb from very high altitudes. As a result of RAF experience with the Fortress, it was determined that there was a need for vast improvements in defensive gunnery, a need for operating the Fortresses in greater numbers in tighter formations for better defensive firepower, and a need for better and more intensive crew training. Nevertheless, their British crews generally were quite pleased with the Fortress I, regarding it as easy to fly, very maneuverable, and aerodynamically stable in the bomb run.
Serial numbers of the Fortress I
USAAC RAF 40-2043 AN518 was WP-B ans is seen in film "Flying Fortress" 40-2044 AN519 40-2051 AN520 40-2052 AN521 40-2053 AN522 40-2055 AN523 40-2056 AN524 40-2057 AN525 40-2060 AN526 was WP-G 40-2061 AN527 40-2064 AN528 40-2065 AN529 40-2066 AN530 was WP-F, which saw action, but survived 40-2068 AN531 40-2069 AN532 40-2071 AN533 40-2073 AN534 40-2075 AN535 40-2076 AN536 40-2079 AN537 was WP-L, later NR-L as seen in photo over convoy with 220 Sqn Coastal CommandSources: