This is gotta be a scam for seeking funding, for a project they know will go nowhere, but which will keep them happily employed for a decade. In his book “Skunk Works”, Ben Rich describes his exploration of an SR-71 replacement concept that was to be hydrogen powered.
They decided it was a bad idea for a lot of reasons. A big one is demonstrated by the space shuttle. The giant external tank is mostly liquid hydrogen. Rich quickly learned you would need an enormous supply on board because they could not be refueled on a long flight. ( ie,,London to Sydney)
Also, it’s very dangerous to store and handle in large quantities. He described his trip to the national bureau of standards to meet with an expert about hydrogen and learn all he could. He describes how horrified that guy was when he asked how hard it would be to run a tank farm storing the stuff.
Hydrogen has it’s fine uses, but i doubt airliner fuel is one of them.
The materials I have studied said the hydrogen-fuel jet project was first. When it was abandoned, The SR-71 took shape, with Ben Rich’s major contribution being the Turbo/ramjet that was finally used.