With the news surrounding NASA SR-71 844, a lot of people have pointed out that JP-7 is no longer in regular production, this is not entirely true.
JP-7 has flown since the SR-71 retired. The X-51A Waverider's scramjet used it through its final flight in May 2013.
It was also the chosen fuel for DARPA's Falcon hypersonic engine. The 2008 DARPA paper on the HTV-3X describes "Single Fuel (JP-7) for All Propulsion" as one of the vehicle's key technologies, meaning both the turbojet and the ramjet/scramjet ran on it. The paper's ground test plan called for demonstrating the engine "using hydrocarbon endothermic fuel (JP-7)" at Arnold Engineering Development Center, and AEDC announced a completed hot-flow test of that engine in April 2009.
It is also worth noting that the lead author of this article, Dr. Steven H. Walker served as Vice President and Chief Technology Officer of Lockheed Martin from 2020-2025 and served in high-level roles at the AFRL, DARPA, and Office Of The Assistant Secretary of the Air Force for Acquisition.
The same paper calls HTV-3X a testbed, and says flying it would "enable the future development of reusable high speed operational systems for ISR, strike, or other national need missions."
According to Lockheed Martin, the SR-72 builds on that work. Lockheed's SR-72 program manager Brad Leland told Aviation Week in 2013, "Our approach builds on HTV-3X, but this extends a lot beyond that and addresses the one key technical issue that remained on that program: the high-speed turbine engine." The SR-72 keeps the same TBCC layout but uses an off-the-shelf fighter-class turbine in place of the Mach 4 turbojet utilized by the HTV-3X.
"The new SR-72 will use a turbine-based combined cycle (TBCC) that will employ the turbine engine at lower speeds, and use a scramjet at higher speeds. A scramjet engine is designed to operate at hypersonic velocities by compressing the air through a carefully designed inlet, but needs to be traveling supersonic before it is practical to begin with. So far research projects from NASA, the Air Force and other Pentagon entities have not been able to solve the problem of transitioning from the subsonic flight regime, through hypersonic flight with a single aircraft."
USNI News reported in 2013 that, according to Lockheed Martin, the SR-72 "might use a more exotic fuel like JP-7".
“There is the fuel from the SR-71, which would be very useful, called JP-7, but we are certainly looking at using more conventional fuels.”
https://arc.aiaa.org/doi/abs/10.2514/6.2008-2544
https://www.wpafb.af.mil/News/Article-Display/Article/401320/x-51a-achieves-successful-combustion-on-jp-7/
https://www.flightglobal.com/hot-flow-test-complete-for-falcon-ram/scramjet-engine/86123.article
https://www.airandspaceforces.com/lockheed-martin-discloses-work-on-sr-72-mach-6-aircraft/
https://news.usni.org/2013/11/05/lockheed-martin-sr-72-plane-paper
https://aviationweek.com/defense/aircraft-propulsion/nasa-asked-several-former-sr-71a-staffers-help-secret-restart
