> what does this test flight prove?
This? Nothing of general consequence. Once XB-1 goes supersonic, which Boom says it’ll do later this year, we’ll get real-world sonic-boom reduction data that could influence the FAA. It will also demonstrate the drag of their nose design, which should inform fuel-burn estimates for their airliner.
Following that, the hurdle is the supercruising engine. The XB-1 uses afterburning J85s to go supersonic. Presumably, getting the FAA to flip on overland bans would unlock the capital needed to finish Symphony [1].