18. June 1934
Boeing engineers began design of a four-engine bomber to meet an Air Corps specification.
28. July 1935
First flight of Boeing Model 299 prototype Flying Fortress.
30. October 1935
Prototype Model 299 destroyed in crash at Wright Field. U.S. Air Force Pilot Major Ployer Hill and Boeing's Chief-Test-Pilot Leslie Turner died on this crash.
2. December 1936
First flight of a "fit for action" Y1B-17.
21. July 1940
First flight of B-17C.
8. July 1941
First Fortress combat mission flown by RAF with Fortress Is against German navy yard at Wilhelmshaven.
5. September 1941
First flight of B-17E, first tailgun and power turret equipped Fortress.
17. August 1942
First Eight Air Force B-17E mission against Rouen.
12. April 1943
Board of officers including five from Eight Air Force and one from the Royal Air Force completed the plan for the Combined Bomber Offensive (CBO) from the United Kingdom against Germany, under which the two services woult coordinate attacks.
17. May 1943
Last (25th) combat mision for the B-17F "Memphis Belle", before its return to the United States for war bond sales.
19. May 1943
First flight of XB-38, a B-17E converted by Lookheed-Vega to use Allison V-1710-89 liquid-cooled engines.
21. May 1943
First flight Of B-17G.
1. November 1943
First 15th Air Force combat mission was a B-17 raid, attacking the La Spezia naval base and railroad bridge at Vezzano.
B-17s in natural metal finish began operations from England, contrasting with earlier camouflaged Fortresses, they had a better top speed.
4. March 1944
First USAAF bombers over Berlin were B-17s from 95th and 100th bomb groups, dropping 67 tons.
24. April 1944
First use of AZON (Azimuth Only) bomb by B-17 in Europe; 15th AF, with mire tactical targets on its list than the Eight AF, tried AZON bombs which had radio device to permit bombardier to steer them in azimuth as they fell toward target. AZON had some utility against specific samll targets like bridges.
9. April 1945
Last Boeing-built Flying fortress, B-17G-110-BO number 43-39508, rolled out of factory with ceremonies. It was delivered to the USAAF four days later - too late for combat.
13. January 1947
Air Force B-17G drone flown remotely, guide by another director B-17, from Eglin, Florida, to Washington D.C., as a demonstration of capability.
14. October 1959
Retired of last US Coast Guard PB-1G Fortress.
Last downing of a USAF target drone B-17.