Boeing B-17 Flying Fortress

• 1. Introduction

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  The Boeing B-17 Flying Fortress earned its name on the 27th of July 1935, one day before its first flight. Seattle Times reporter Richard Williams watched Boeing's new prototype bristling with machine guns on the runway. He called it a "15-ton flying fortress" in a photo caption, and the label stuck. Boeing recognized the value of the nickname right away and had it trademarked.

  It became the third-most produced bomber in history, trailing only the Consolidated B-24 Liberator and the German Junkers Ju 88. Yet the very prototype that inspired that name crashed less than a year after it first flew. The crash took two men's lives and cost Boeing an early production contract. From that rough start came a bomber the Army Air Forces would lean on across two oceans of war.

  What actually went wrong on that test flight. How a bomber once judged too expensive for its own service came to shape American strategy over Europe and the Pacific. Why crews who flew both the B-17 and the more numerous B-24 tended to trust the Fortress more. Those threads run through everything that follows.

• 2. A Costly Trial

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  On the 8th of August 1934, the Army Air Corps requested proposals for a new multi-engine bomber to replace the Martin B-10. The Air Corps wanted a plane able to reinforce forces in Hawaii, Panama, and Russia. It had to carry a useful bomb load at 10,000 feet for 10 hours at 200 mph, with a hoped-for range of 2,000 miles. Boeing, Douglas, and Martin were each invited to compete, testing their designs in a fly-off at Wilbur Wright Field in Dayton, Ohio.

  Boeing built its entry, the Model 299, entirely at its own expense. Engineers E. Gifford Emery and Edward Curtis Wells combined features from the company's experimental XB-15 bomber and its 247 transport airliner. Armed with five .30 caliber machine guns and able to carry up to 4,800 pounds of bombs, it flew for the first time on the 28th of July 1935, with chief test pilot Leslie Tower at the controls. Three weeks later, on the 20th of August 1935, it flew from Seattle to Wright Field in nine hours and three minutes, averaging 252 mph. At the fly-off itself, the four-engine Boeing outperformed the twin-engine Douglas DB-1 and Martin Model 146.

  That March, Army Chief of Staff Douglas MacArthur had created a new GHQ Air Force and put Brigadier General Frank Maxwell Andrews in charge of it. Both men believed four-engine aircraft like the B-17 suited the Air Corps' emerging doctrine better than shorter-range, twin-engine designs. Procurement officers agreed even before the competition ended, and proposed buying 65 of the new bombers.

  On the 30th of October 1935, a test flight was set to measure the prototype's rate of climb and service ceiling. Major Ployer Peter Hill commanded, on his first flight in the Model 299, with Lieutenant Donald Putt as copilot and Leslie Tower riding along in an advisory role. Test observer John Cutting and mechanic Mark Koegler were also aboard. Soon after takeoff the plane stalled, spun into the ground, and burst into flames. Hill died within hours; Tower died on the 19th of November 1935. Investigators found the control-surface gust lock had never been released. As historian Doyle later put it, "The loss of Hill and Tower, and the Model 299, was directly responsible for the creation of the modern written checklist used by pilots to this day."

  Because the crash disqualified the Model 299 before it could finish evaluation, cost tipped the balance against it. Douglas quoted $58,200 per aircraft for an order of 220, against Boeing's $99,620. MacArthur's successor, Malin Craig, canceled the order for 65 YB-17s and bought 133 Douglas B-18 Bolos instead. In October 1938, Secretary of War Harry Hines Woodring ruled that no four-engine bombers would be purchased for 1939 either.

  Even so, the Air Corps had been impressed enough by the prototype to act. Through a legal loophole, it ordered 13 YB-17s on the 17th of January 1936, later redesignated Y1B-17, for further service testing. The 13th of those aircraft went to Wright Field for flight testing, while a 14th, still under construction, would soon carry engine changes that reshaped the type's whole future.

• 3. An Airframe Reborn

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  The fourteenth Y1B-17, originally built only for ground testing, gained four General Electric turbo-superchargers designed by engineer Sanford Moss. They forced high-pressure air into the Wright Cyclone engine's supercharger using exhaust gases. Turbocharger problems delayed its first flight until the 29th of April 1938, and it was delivered to the Army on the 31st of January 1939 as the Y1B-17A. It reached 311 mph and a service ceiling above 38,000 feet, against 239 mph and 27,800 feet for the standard Y1B-17.

  Ten more aircraft, ordered as the B-17B in late 1937, added larger flaps, a bigger rudder, and a ten-panel plexiglass nose. They were delivered in five small batches between July 1939 and March 1940. The following B-17C swapped bulged gun blisters for flush window openings and a single "bathtub" gun gondola on the lower fuselage, resembling the ventral turret on the German Heinkel He 111.

  The B-17E, first flown on the 5th of September 1941, was the first version built mainly for offense rather than defense. Its fuselage was stretched by 10 feet, a tail gunner's position was added, and Sperry dorsal and ventral ball turrets went in. These changes raised the aircraft's weight by 20 percent.

  By the time the B-17F became the Eighth Air Force's main bomber in 1943, its nose glazing had been enlarged and made nearly frameless for better forward vision. Two experimental variants branched off around this time. The XB-38 tested Allison V-1710 engines but crashed on its ninth flight, ending the concept. The YB-40 added extra turrets and more than 11,000 rounds of ammunition but grew too heavy to keep pace once bombs were dropped, and it was phased out by July 1943.

  The definitive B-17G raised the gun count from seven to thirteen. With 8,680 built, it became the most numerous variant, and the last one left the line, built by Lockheed, on the 28th of July 1945. In total, Boeing, Douglas, and Vega built 12,731 B-17s between 1935 and 1945. Some late B-17Gs were fitted with television cameras and 20,000 pounds of explosives, becoming radio-controlled "Aphrodite" drones aimed at fortified German bunkers under an operation approved on the 26th of June 1944; it caused little damage, cost two pilots their lives, and was scrapped in early 1945. By 1944, the aircraft that had once flown as an unarmed prototype now carried thirteen guns into the heart of German airspace.

• 4. Bombing By Day

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  In early 1940, the Royal Air Force agreed to acquire twenty B-17Cs, giving them the service name Fortress Mk.I. Their first operation, against Wilhelmshaven on the 8th of July 1941, achieved little. On the 24th of July 1941, three B-17s of 90 Squadron attacked German warships Gneisenau and Prinz Eugen at Brest from 30,000 feet, meant as a diversion for lower-flying bombers, but met no opposition at all. By September, the RAF had lost eight B-17Cs and abandoned Fortress I daylight raids over poor performance, shifting survivors to Coastal Command for maritime patrol. A Fortress IIA from No. 206 Squadron sank the U-boat U-627 on the 27th of October 1942, the first of eleven U-boat kills credited to RAF Fortresses.

  The Air Corps, renamed the USAAF on the 20th of June 1941, pressed ahead with daylight bombing anyway. It relied on the secretive Norden bombsight, nicknamed the "Blue Ox," which let a bombardier calculate the release point during the final run. The first Eighth Air Force heavy raid came on the 17th of August 1942, when twelve B-17Es of the 97th Bomb Group, led by Major Paul Tibbets with Brigadier General Ira Eaker observing, hit rail yards at Rouen-Sotteville in France, escorted by RAF Spitfires.

  At the Casablanca Conference in January 1943, American and British commanders combined their strategies into the Combined Bomber Offensive. The USAAF would bomb by day and the RAF by night. General Ira Eaker's Eighth Air Force targeted German fighter plants, engine factories, and ball-bearing works, opening attacks on Bremen and Recklinghausen in April 1943.

  On the 17th of August 1943, 230 B-17s attacked the ball-bearing factories at Schweinfurt and met roughly 300 Luftwaffe fighters. Combined with a same-day raid on Regensburg, 60 bombers were lost that day. A second Schweinfurt raid on the 14th of October 1943, remembered as "Black Thursday," cost 77 B-17s outright and left 122 more damaged. Of 2,900 crewmen flying that day, about 650 did not return, and only 33 aircraft landed undamaged.

  Losses like that forced the USAAF to suspend deep daylight raids until escort fighters could cover the whole route. A third Schweinfurt raid on the 24th of February 1944 opened what became known as "Big Week." North American P-51 Mustangs and Republic P-47 Thunderbolts, fitted with extended-range drop tanks, escorted bombers to their targets and back. The loss rate fell below 7 percent, though 247 B-17s were still lost across 3,500 sorties. By the 27th of April 1945, two days after Europe's last heavy bombing mission, losses had dropped so low that replacement bombers stopped arriving altogether.

• 5. War Over The Pacific

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  On the 7th of December 1941, twelve B-17s en route to reinforce the Philippines flew straight into the attack on Pearl Harbor. Co-pilot Leonard "Smitty" Humiston first mistook the anti-aircraft fire for a 21-gun salute welcoming the bombers in. Diverted to Bellows Field, one aircraft overran the runway and was strafed, taking more than 200 bullet holes; ten of the twelve survived the attack.

  At Clark Field in the Philippines, the Far East Air Force had 35 B-17s when word of Pearl Harbor arrived. General Lewis Brereton's plan to bomb Japanese airfields in Formosa was overruled by General Douglas MacArthur. Delays from confused reporting meant Japanese bombers destroyed half the Far East Air Force's aircraft on the ground within days.

  On the 10th of December 1941, Colin Kelly reportedly crashed his B-17 into the Japanese battleship Haruna, an action later found to have actually near-missed the cruiser Ashigara. Kelly held his burning aircraft steady so his crew could bail out, before it crashed about six miles from Clark Field, earning him a posthumous Distinguished Service Cross. Japanese ace Saburō Sakai, credited with the kill, came away respecting the bomber's ability to absorb punishment.

  The Fifth Air Force's B-17s, tasked with disrupting Japanese sea lanes, initially hit only about 1 percent of their targets bombing from high altitude. Their biggest success came at the Battle of the Bismarck Sea. On the 2nd of March 1943, six B-17s of the 64th Squadron used skip bombing at 10,000 feet against a convoy carrying 1,200 troops, sinking one transport and damaging two others, the Teiyo Maru and Nojima. The next day, thirteen B-17s bombed the convoy again from 7,000 feet, scattering it and drawing Zero fighters that clashed with escorting P-38 Lightnings.

  By September 1942, at their Pacific peak, 168 B-17 bombers served in the theater. General Henry Arnold judged the type unsuited to Pacific operations and began replacing it with B-24s, and later B-29s, ending B-17 combat missions there after little more than a year. Special airdrop B-17s later supported Australian commandos fighting near the Japanese stronghold at Rabaul, the very target the type had once been sent to bomb.

• 6. Built To Endure

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  Early B-17s carried just four .50 caliber machine guns plus a single .30 caliber gun in the nose of the B-17C. By the definitive B-17G, that had grown to thirteen .50 caliber guns. A 1943 USAAF survey found that more than half of the bombers shot down by Germans had straggled from the main formation.

  To fix that vulnerability, the Air Corps developed the staggered combat box, letting every B-17 in a group cover its neighbors with crossfire. Luftwaffe pilots likened attacking one to facing a fliegendes Stachelschwein, a "flying porcupine" bristling with guns from every direction. Assembly ships, painted in distinctive schemes, helped bomber groups form up faster before missions.

  Eighth Air Force pilot Wally Hoffman put it plainly: "The plane can be cut and slashed almost to pieces by enemy fire and bring its crew home." Historian Martin Caidin described one B-17 that collided in midair with a Focke-Wulf Fw 190, losing an engine and both stabilizers, yet still flew home with its crew unharmed.

  German pilots found they needed about 20 hits with 20 mm shells from the rear to bring a B-17 down, but only four or five hits from the unarmored front. Later Fw 190 "Sturmbock" variants carried four 20 mm cannon, and by 1944 some carried 30 mm MK 108 cannon that could finish a bomber in just a few hits. The Me 262 jet, firing MK 108 shells or R4M rockets loaded with Hexogen explosive, could down a B-17 with one hit from outside the bombers' own gun range.

  American countermeasures called Window and Carpet jammed German radar, cutting flak's effectiveness by as much as 75 percent and saving an estimated 450 bombers. Germany would soon turn a number of captured Flying Fortresses against their own kind, studying exactly these weaknesses from the inside.

• 7. Behind Enemy Lines

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  Germany captured and refurbished roughly 40 B-17s during the war, painting on Balkenkreuz crosses and swastika tail markings, and returned about a dozen to the air. These were used to study the bomber's weak points and train Luftwaffe interceptor pilots in attack tactics.

  Others, disguised under the cover names Dornier Do 200 and Do 288, flew for the special-duties unit Kampfgeschwader 200 as long-range transports. They carried out agent drops and supplied secret airstrips across the Middle East and North Africa, always in full Luftwaffe markings. One KG200 B-17, marked A3+FB, was interned by Spain after landing at Valencia airfield on the 27th of June 1944, and it stayed there for the rest of the war.

  The Soviet Union never received B-17s through official war aid, yet acquired at least 73 of them after they landed with mechanical trouble or battle damage near Poltava. Soviet crews restored 23 to flying condition and grouped them in the 890th Bomber Regiment, though they never flew in combat. In 1946, the unit moved to a Kazan factory to help reverse-engineer the Boeing B-29 as the Tupolev Tu-4.

  In October 1943, a B-17F, tail number 25841, developed engine trouble after a raid over Germany and landed in Switzerland, where its American crew was interned. The Swiss Air Force flew the bomber for the rest of the war, repainting its topside dark olive drab while keeping its original light gray underside, and marking it with the Swiss white cross.

  Japanese technicians rebuilt three abandoned B-17 wrecks, one "D" model and two "E" models, salvaged from the Philippines and the Java East Indies in 1942. Flown to Japan's Air Technical Research Institute at Tachikawa, they were used in pilot training, tactics development, and propaganda films. One was photographed late in the war and misidentified as "Tachikawa 105" until after the war ended. No trace of any of the three was ever found once Allied forces occupied Japan. Whatever became of those three airframes, the type they belonged to still had years of service left to fly, just not as a bomber.

• 8. After The Guns Fell Silent

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  Strategic Air Command, established in 1946, still flew reconnaissance B-17s, first designated F-9 and later RB-17, until 1949. Most of the wider fleet, though, was ferried back across the Atlantic after the war and sold for scrap.

  The Navy acquired 48 former Army B-17s, designating them PB-1, a name last used in 1925 for an experimental Boeing flying boat. Thirty-two became PB-1Ws, fitted with a large under-fuselage radome housing an AN/APS-20 search radar for airborne early warning, serving until 1955. In July 1946, sixteen more went to the Coast Guard as PB-1Gs, flying air-sea rescue and iceberg patrol until the last was withdrawn on the 14th of October 1959.

  CIA front companies, including Civil Air Transport and Intermountain Aviation, flew stripped, black-painted B-17s on covert agent-drop missions over the People's Republic of China, launched from Taiwan. One of these aircraft, N809Z, later carried out Operation Coldfeet on the 28th of May 1962, using a Fulton Skyhook system to retrieve two officers who had parachuted onto an abandoned Soviet arctic ice station. That same aircraft performed a Skyhook pickup in the 1965 James Bond film Thunderball before eventually going to the Collings Foundation in 2015.

  Surplus B-17s also flew as drones during the 1946 Operation Crossroads atomic tests, passing through mushroom clouds to sample the atmosphere without risking a crew. A hundred and seven were eventually converted to drones or drone controllers. The type's last operational USAF mission came on the 6th of August 1959, when a QB-17G served as a missile target over Holloman Air Force Base.

  Pilots who flew both types tended to prefer the B-17 over the more numerous B-24, citing steadier handling and electrical systems less vulnerable to damage than the Liberator's hydraulics. Eighth Air Force commander Jimmy Doolittle pushed to equip his force with B-17s and P-51s alone, valuing the simplicity of running fewer aircraft types. His own statisticians found the Fortress survived missions at a notably higher rate than the B-24.

  As of October 2025, three Flying Fortresses remain able to fly, among roughly 50 surviving in storage or on static display. The oldest, a B-17D called The Swoose, flew combat over the Philippines on the first day of America's involvement in the war, and is now being prepared for display at the National Museum of the United States Air Force. In 2022, one of the survivors, Texas Raiders, was destroyed in a midair collision with another warbird at an airshow in the United States.