The 1934 precursor to the Osprey

Well, almost an Osprey. They cylinders would have to be made of balsa wood for the thing to get off the ground. Photo credit: James Vaughn FLickr x-ray delta one

Maybe now, with the reliability of electric engines, it's time to reevaluate the merits of the Custer Channel Wing...

I wonder when the first hydrogen jet engine will come. Or liquid gas.

LNG fueled aircraft turbine engines have been researched, and even test flown in the late-1980s. A more recent study was done by BMW & Airbus during the early 20-teens, though I do not think they actually flew any aircraft using a LNG fueled turbine. Maybe they have since then. From what I read it seemed quite practical and relatively simple to modify an existing jet engine design within certain parameters.

There have been a significant number of LNG fueled turbine powered electricity generation plants for some time (since the late-1990s?). Siemens and GE, for example, both make 'H' class turbines for electric power generation.

EDIT: I should have been more specific. From what I read it seemed quite practical and relatively simple [as far as running the engine on LNG] . . .
Storage and energy density of the LNG are the main problems.