There is some discussion on problems using hydrogen for aircraft in the Ben Rich book "Skunk Works", Lockheed were looking at it [1] before they developed the S

There is some discussion on problems using hydrogen for aircraft in the Ben Rich book "Skunk Works", Lockheed were looking at it [1] before they developed the SR-71. [1] https://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan https://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan