Liquid Hydrogen is not a lot of fun. Anything with an 700:1 expansion ratio is a stored energy hazard in and of itself, but because it's cryogenic it also means the cumulative daily loses in tanks where cooling is not actively maintained will be a constant annoyance.

They seem intentionally coy about how the 523 miles where flown, seemingly just above Marina, CA. They have requested that flight tracking not be publicly shown on flight aware.