You don't need a "complicated" cryogenic setup. You just need insulated tankage. But it won't fit in the wings, so you need new airframes or fuel nacelles. We

You don't need a "complicated" cryogenic setup. You just need insulated tankage. But it won't fit in the wings, so you need new airframes or fuel nacelles. We have a very great deal of experience with fuel nacelles already, because that is what a "drop tank" looks like; you just omit the "drop" complication. The advantages over inboard tankage are safety, possible retrofitting of existing fleets, and short plumbing runs. Once LH2 aircraft are used on any route, kerosene craft will be wholly unable to compete, even without carbon taxes. Carbon taxes could be spent on accelerating the transition.