Thanks for your reply t43562.
So, let us cut to the chase....There are Military possibilities for partial/air breathing Scramjet etc high altitude/high speed vehicles that must incorporate cryogenic elements. However, the technologies are underdeveloped, expensive and not yet crucial so, it gets back-burnered and funded from misdirected technology development, and sci-fi spaceplane smoke and mirror funding.
Good luck with your (notional) spaceplane.
BTW, Charge air cooling of subsonic commercial aircraft gas turbines is already proven to be inefficient, even if the heat exchanger was weightless.
OAP