A post[0] from a couple days ago says they've reach ~0.95 Mach, ~43k feet, 10 flights, 11.7 hours of flight time with the longest flight at 1.7 hours.
[0]:https://www.lockheedmartin.com/en-us/news/features/2026/X-59...
And there's a lot of private companies contributing[1]. But makes me wonder where Boom/Hermeus/Astro Mechanica etc fit in.
[0]:https://www.nasa.gov/quesst-the-mission/
[1]:https://www.nasa.gov/wp-content/uploads/2019/05/companies-co...