The Boeing B-17 Flying Fortress was a four-engine heavy bomber aircraft developed in the 1930s for the United States Army Air Corps (USAAC). 

The B-17 was primarily employed by the United States Army Air Forces (USAAF) in the daylight precision strategic bombing campaign of World War II against German industrial and military targets. The United States Eighth Air Force, based at many airfields in southern England, and the Fifteenth Air Force, based in Italy, complemented the RAF Bomber Command's nighttime area bombing in the Combined Bomber Offensive to help secure air superiority over the cities, factories and battlefields of Western Europe in preparation for the invasion of France in 1944. The B-17 also participated to a lesser extent in the War in the Pacific, early in World War II, where it conducted raids against Japanese shipping and airfields.

The first prototype, called the Model 299. Slick and fast for the time (1935), but several things would drop before service (including the cool bubble turrets).

FUCK. Model 299 crashed on 30 Oct 1935.

The famous Memphis Belle, the first aircraft to return all it's crew safely after 25 missions, at which point it returned to the US for a Bond selling tour. But in the real world... another aircraft completed 25 missions less than a week before! Hell's Angels (MUCH better name as well) finished 25 missions, then went on to complete 48 total without returning prior to dropping its payload.

December 7th, 1941--Pearl Harbor. This photo is of Japanese 'Val' bombers was taken from a B-17 on reconnaissance.

Japanese A6M2 Zero flying above a shot-down US fighter, also taken by a B-17 during the Pearl Harbor attack.

The B-17C AAF S/N 40-2074 was shot up by the Japanese, Although one crewman was killed by the Zero's attack, and was able to land (somewhat) safely at Hickam Field. An onboard fire burnt the aircraft in two shortly after landing on 7 December 1941.

German fighters would fly head on to attempt to take out bombers. This particular aircraft was struck by an enemy fighter's wing! Close-up of the damage to Boeing B-17F-5-BO (S/N 41-24406) "All American III." The left horizontal stabilizer was torn completely off, and the aircraft was nearly cut in half by the collision.

From its pre-war inception, the USAAC (later, the USAAF) touted the aircraft as a strategic weapon; it was a potent, high-flying, long-range bomber that was able to defend itself, and to return home despite extensive battle damage. Its reputation quickly took on mythic proportions, and widely circulated stories and photos of notable numbers and examples of B-17s surviving battle damage increased its iconic status.

The severely damaged B-17F bomber "All-American" of 97th BG of US 414th BS continues to fly after an attacking  and collision with a German Bf 109 fighter over Tunis in North Africa, 1 Feb 1943. The B-17 flew home and landed in this condition safely without major injuries to any of the crew members. It was repaired and put back in action.

Me-410 BARELY missing a B-17. Note the 50mm cannon sticking out of the front!

Severely damaged tail, but still flying home...

American bomber Boeing B-17G-90-BO (№ 43-38594) "Lady B Good" from the 749 Squadron, 457 th Bomb Group of the 8th Air Force U.S. Air Force. This aircraft was under the control of 1st Lt. Craig Grison (Craig P. Greason) was attacked by a German jet fighter Me-262 during a raid on Berlin March 18, 1945 The pilot managed to fly the aircraft back to base in England. To repair the plane, we had to completely replace the left wing. It was the second time in less than two months for the machine when it received serious injuries during raids on Berlin. Prior to that, "Lady B Good" was damaged by antiaircraft artillery February 3, 1945, then the plane made an emergency landing in Belgium.

Chemtrails over Europe* *there are no such things as chemtrails. Even propeller aircraft form contrails at the right altitudes and conditions, where the exhaust condensation is quickly condensing.

The tail of the bomber Lockheed / Vega B-17G-5-VE (№ 42-39867) damaged by ground fire during a raid on Frankfurt, January 24, 1944. Stern shooter Roy Urich was thrown overboard explosion, but he survived and was captured by the Germans. This aircraft was repaired and re-joined the 100th Bomb Group.

Bomber B-17G-25-DL "Sweet Pea" (serial number 42-38078) received a direct hit by flak during a raid on the Hungarian city of Debrecen 21.09.1944 . Despite the critical damage, the pilot Guy Miller (Guy M. Miller) was able to return to Amendola airfield in Italy. Radio operator Anthony Ferrara (Anthony Ferrara) and the shooter James McGuire (James F. Maguire) were wounded, the shooter Elmer Bass (Elmer H. Buss) was killed immediately, but stern shooter James Totti (James E. Totty) died of his wounds at the time of return to the base. Surprisingly, the plane was repaired and put back into service.

IIRC this was the result of a bomb falling from a plane above, the aircraft is inverted and uncontrollable.

Damaged aircraft losing control.

A couple hundred B-17's waiting for service. The US produced well over 12,000 total for the war!

Top view of the ball turret. This was the most dangerous position, as the motors often jammed due to electrical failure. It was only accessible in certain positions, so if it jammed when you were not sitting perfectly you were stuck. There are many stories where the B-17 could not retract the gear and had to land on the turret while it was still manned... For that reason they retracted on B-24's (though they still sometimes jammed).

How a gunner had to sit in the turret. How to get in:

My balls. Look at them.

Engine smoking heavily as an aircraft returns to base.

The collision of two B-17 bombers (Boeing B-17G-75-BO serial number 43-38030 and the Boeing B-17G-80-BO serial number 43-38133) of the 305th U.S. Air Arm in the skies over the English countryside Turley (Thurleigh). The collision occurred in conditions of poor visibility when returning aircraft bombing of Hanover. The crews of both aircraft (18 patients) died.

B-17F destroyed by a ME-262 (Germany's first jet fighter)

Cockpit. There are several updated components as this is an aircraft still flying.

(Incendiary?) bombs over Japan. The US designed special bombs to burn up as much of the cities as possible, since much of Japan was basically made of paper at the time. Horrible wartime fact: around 50% of Tokyo was destroyed in the firebombings, with as many as 200k casualties (more than either atomic bomb). The fires got so hot that people jumped into reservoirs and canals in the city, where they were boiled alive.

B-17G 43-38172 of the 8th AF 398th BG 601st BS which was damaged on a bombing mission over Cologne, Germany, on 15 October 1944 by Heavy flack damage; the bombardier was killed 

Captured B-17F-27-BO in Luftwaffe markings being tested, the USAAF-named "Wulfe-Hound", 41-24585, of the 360th BS/303rd BG, downed on 12 December 1942 near Leeuwarden, Netherlands, while on a raid on Rouen, France, the first Flying Fortress to fall intact into German hands. Operated byKampfgeschwader 200 from March 1944.

This Philippines-captured USAAF Boeing B-17D, in Japanese livery, was flown to Japan for technical evaluation.

And the US testing some captured V-1 'Buzz bombs'.

B-17G Fortress “Liquid-8-Or” of 569th Bomb Squadron dropping cases of “10 in 1” rations into Holland during Operation Chowhound aimed at breaking the famine in western Holland, May 1 or 3 1945.

B-17G Fortress “Mizpah” took a direct AAA hit in the nose on mission to Budapest, 14 Jul 1944. 2 were killed instantly but the pilot held her level long enough for crew to get out & become POW's. The aircraft crashed near Dunavecse, Hungary "Mizpah" is a type of emotional bond between two people separated, either physically or by the death of one of the persons. Mizpah means 'the Lord watch between me and thee when we are absent from one another'.

Lockheed/Vega B-17F-20-VE, serial number 42-5786) 840-483-th squadron of the bombardment on fire after being hit over Kakanj, ( Bosnia and Herzegovina) ex Nis Yugoslavia on the 25th April 1944.

Combat box formation during bombing missions for a squadron of 12 B-17s 1. Lead Element 2. High Element 3. Low Element 4. Low Low Element

Formations would fly extremely close to one another and all release their payload at the command of the lead aircraft, but sometimes they flew too close... The rationale behind this was protection from enemy fighters (more guns in a condensed area) and to maximize effect of carpet bombing.

Complete series from the previous picture.

Another view of close formation bombing.

B-17 crash landed in England. Above the window for the rear gunner you can see his nickname, Pappy. Along with many other tail gunners, Pappy was KIA.

Heavy flack at operation Pointblank. Flack is basically small bombs that would burst around the aircraft, showering it with shrapnel.

B-17's from the 390th Bomb Group over Germany. "Skippy" (DI-F) Douglas-Long Beach B-17F-45-DL Flying Fortress s/n 42-3329 crashed during formation on February 5,1944 due to engine failure. It came down at Salehurst, Sussex. Crew bailed out safely.

Doing a low flyby for the cameras!

Crews examine flak damage to B-17G Fortress at RAF Bassingbourn, Cambridgeshire, England, UK. Damage sustained on mission to Munich, Germany, Jul 6 1944. Note "Mickey" pathfinder radar dome in place of ball turret.

B-17 Flying Fortresses from the398th Bombardment Group fly a bombing run to Neumünster, Germany, on 13 April 1945. On 8 May, Germany surrendered, and Victory in Europe Daywas declared.

Interior view of gunner stations.

This is a good report on the Enemy Attacks approach, I thought that the attached image would add to the information.  This is the German study of the B-17 Flying Fortress fire power.  Also the points most vulnerable to Cannon Fire.  The small printing on the attachment is all printed in German so can't tell what it says but by looking at the overall view, you know what they mean.

The most unusual conversion of the B-17G was the JB-17G converted to an engine test bed. The nose section was removed and replaced with a strengthened mount for a fifth engine.

With aservice ceiling greater than any of its Allied contemporaries, the B-17 established itself as an effective weapons system, dropping more bombs than any other U.S. aircraft in World War II. Of the 1.5 million tonnes of bombs dropped on Germany and its occupied territories by U.S. aircraft, 640,000 tonnes were dropped from B-17s

The B-17 was a staple of the Allied offensive, though it overshadowed many other aircraft. For example, the B-24 dropped more bombs during the war, was faster, had longer range and more were produced... but few aircraft took as much damage and returned as the B-17.