On August 31, 1940, Pennsylvania Central Airlines Flight 19, a new Douglas DC-3, was flying from Washington, D.C. to Detroit with a stopover in Pittsburgh. While the aircraft was flying near Lovettsville, Virginia at 6,000 feet (1,800 m) and approaching the West Virginia border, Flight 19 encountered an intense thunderstorm. Numerous witnesses reported seeing a large flash of lightning shortly before it nosed over and plunged to earth in an alfalfa field. With limited accident investigation tools at the time, it was at first believed that the most likely cause was the plane flying into windshear, but the Civil Aeronautics Board report concluded that the probable cause was a lightning strike. U.S. Senator Ernest Lundeen was among the 21 passengers and 4 crew members killed. Also on board were "a Special Agent of the FBI, a second FBI employee, and a prosecutor from the Criminal Division of the U.S. Department of Justice." At the time of the crash, the FBI was investigating Sen. Lundeen's ties to George Sylvester Viereck, a top German agent working in the U.S. to spread pro-Nazi and antisemitic propaganda.