Boeing B-47 Stratojet

The Boeing B-47 Stratojet is a retired American long-range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircraft. The primary mission of the B-47 was as a nuclear bomber capable of striking targets within the Soviet Union.

Development of the B-47 can be traced back to a requirement expressed by the United States Army Air Forces in 1943 for a reconnaissance bomber that harnessed newly developed jet propulsion. Another key innovation adopted during the development process was the swept wing, drawing upon captured German research.

Source: Wikipedia