Short answers, pulled from the story.
The Army Air Corps ordered 13 more aircraft for evaluation in 1936 through a legal loophole. Twelve of these units were delivered to the 2nd Bombardment Group at Langley Field in Virginia by March 1937.
Boeing built 12,731 B-17 Flying Fortresses across three factories between 1941 and May 1945. Boeing Plant 2 in Seattle handled initial production runs while Lockheed-Vega operated out of Burbank, California and Douglas Aircraft manufactured additional airframes at their Long Beach facility.
Sixty Fortresses were shot down over Germany while another five crashed approaching Britain on the 14th of October 1943. One hundred twenty-two additional bombers required repairs before their next missions and about six hundred fifty men from nearly three thousand crews did not return home.
The first Eighth Air Force heavy bomber raid over Europe occurred on the 17th of August 1942 when twelve B-17Es attacked railroad marshalling yards at Rouen-Sotteville in France under Major Paul Tibbets command.
Four B-17 Flying Fortresses remain airworthy as of January 2025 according to current records. The oldest surviving Fortress is The Swoose built in 1940 and flown in combat during Philippines campaign which resides currently in National Air and Space Museum collections awaiting restoration display.