It appears that they are taking advantage of the following:
- it is legal for someone to hire a commercial pilot to fly them in an airplane the hirer (not the pilot) provides under part 91
- it is legal for an airplane owner to lease out their airplane to a third party if the third party flies themselves or hires their own commercial pilot
- blackbird is arranging two independent services that happen to coincide into a single point to point flight.
They have $10m of funding from a legit VC that isn’t easily fooled so they probably aren’t being completely naive about the regs.
That all being said, the FAA is king of the air and they may decide that while there isn’t currently an FAR being directly violated, this conflating of two technically legal things ends up violating the spirit of the FARs and write up a new ref or opinion that kills the concept.