And what might that be?
If a satellite constellation provides (near or actual) real time observation in ESM, airborne radar, visual/infrared or hyperspectral, weather, and gamma-ray/radiation detection...what exactly is missing here? Nothing for a strategic reconnaissance strike system, that's for sure. A plane takes time to fuel, a hypersonic aircraft probably has a fairly significant turnaround time, probably longer than an hour and a half or so. So it's not faster than a (very meager coverage) satellite, that's for sure, much less the 20-45 minute revisit times of some commercial constellations,
or future military constellations.
There are cases for airborne observers obviously, but they absolutely have no need (nor desire) to be hypersonic airbreathers. Airborne reconnaissance aircraft desire to be subsonic, both for reasons of fuel efficiency and infrared stealth, and very low-observable in the radar regimes. This means large, to avoid being detected by OTH-B or OTH-R radars, so nothing particularly small like F-35, which means large mass for MASINT sensors to detect airborne particulates of radioactive particles indicating NUDET and possibly something like Gorgon Stare to provide all aspect IR/visual observation, as well as radars and fuel for long loiter times and wide area detection of mobile vehicles.
Being very fast is detrimental to reconnaissance aircraft obviously, but it's useful for bombers and more specifically bombers' weapons.
It's why SR-71 itself had radar stealth built-in, and since it existed before orbital infrared targeting/tracking, the problem of going fast was non-existent and itself to evade detection by potentially exceeding the speed gates of extremely early SAM systems like the S-25 Berkut. Naturally this was flubbed before the Blackbird even flew because electronics caught up to it and the Soviets had little to no problems scrambling interceptors or attaining weapons grade locks on Blackbirds skirting their borders, so SR-71's undetectability was made more detrimental by its high speed.
Of course a hypersonic nuclear weapon has no particular desire to be unknown to its opponents. It merely has to evade SAMs. Which is why speed is extremely useful for a strategic nuclear weapon but absolutely dreadful for a reconnaissance system.