Boom Supersonic conducted today a fourth and successful Boom XB-1 test flight, this time reaching an altitude of 16,150 feet and a speed of Mach 0.617 (about 313 knots equivalent airspeed) during tests for flutter, g-forces, handling, and landing gear. The proof-of-concept XB-1 is helping educate Boom Supersonic on how to build and test supersonic aircraft in the lead-up to building Boom Overture.