180201-N-ZB537-0005 PATUXENT RIVER, Md. (Feb. 1, 2018) Dan Levin, F-35 Pax River Integrated Test Force, pilots BF-3 on its 691st flight for a flutter and buffet test mission at Naval Air Station Patuxent River with external weapons. This flight, shown with external 2,000 pound and 1,000 pound GBUs and AIM-9x weapons, is one of the final flight tests for the F-35B in the system development and demonstration phase. (U.S. Navy photo by Dane Wiedmann/Released)