Another smooth landing. XB-1 flight four overview: ✅New max speed: Mach 0.617 ✅First use of the flutter excitation system (FES) in flight ✅Applied elevated g-forces of 2.78g in preparation for supersonic flight ✅Landing gear retracted and extended at 225 KIAS Learn more about XB-1’s fourth flight as test flights continue to speed up: https://boomsupersonic.com/flyby/xb-1-live-blog-flight-test-program | Boom Supersonic