Langley Field, Virginia. YB-17 bombardment squadron. Every note from the power plants of the big planes has a meaning for the men of this bombardment squadron. A maintenance crew listens alertly while the pilot of a mighty YB-17 bomber warms up the first of his four powerful engines for a takeoff from Langley Field, Virginia

The Boeing B-17 Flying Fortress is a four-engine heavy bomber developed in the 1930s for the United States Army Air Corps. Although Boeing lost the contract because the prototype crashed, the air corps was so impressed with Boeing's design that it ordered 13 more B-17s for further evaluation. The B-17 was primarily employed by the United States Army Air Forces in the daylight precision strategic bombing campaign of World War II against Germany. 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 Japan.