NASA's X-59 hits mission cruise speed on second supersonic flight

NASA's X-59 experimental jet hit Mach 1.4 at 55,000 feet on June 12 — the precise speed and altitude it will use during real-world noise surveys over US communities. The milestone came just one week after the aircraft crossed the sound barrier for the first time, reaching Mach 1.1 at 43,400 feet on June 5. Both flights mark concrete progress toward a mission that could rewrite the rules on supersonic flight over land for the first time since 1973.

The quiet thump

The X-59 is designed to replace the traditional sonic boom — a sharp, startling crack that caused regulators to ban overland supersonic flight in the US more than 50 years ago — with what NASA calls a "quiet sonic thump." The target is around 75 decibels at ground level, compared to the Concorde's boom of over 100 dB. To put that in perspective, 75 dB is roughly the volume of a passing car.

During current tests, the X-59 flies alongside a second research aircraft that produces a conventional sonic boom, giving engineers a direct acoustic comparison. The next step is a full verification of the X-59's acoustic signature before NASA moves into the Quesst mission phase, per the NASA Quesst blog.

The regulatory stakes

The X-59 isn't just a flight test program — it's a regulatory argument. The FAA's ban on supersonic overland flight has stood since 1973 and is based on speed limits, not noise thresholds. NASA's plan is to collect public response data from communities overflown during Quesst, then hand that data to the FAA and international body ICAO to build new noise-based standards.

Congress is already moving. The House passed the Supersonic Aviation Modernization Act in March 2026, which would push the FAA to replace the speed-based ban with a noise-based framework. The timeline for that rule-making is tied directly to the X-59's test schedule, reports TechTimes.

Commercial interest is real. Boom Supersonic has over 130 pre-orders for its Overture airliner, but the company needs regulatory clarity before it can commit to a commercial launch date. The X-59's community noise data is effectively the key that unlocks — or delays — the entire post-Concorde industry.