I think Boring Company Tunnels should handle city trips, some short-haul trips; possibly Starship long haul (though mildly terrifying prospect, I'd like to understand the forces on a person).
It's medium haul across seas that interests me most (initially cargo, later passengers). Take off is where the power is used, cruising at high altitude (low air pressure, air resistance, no worries about getting enough oxygen for engines), so medium haul, probably a small frontal area, long body or bullet shaped form rather than wide bodied should be a sweet spot.
I don't see much work being done on this area.
Any info I've missed? I'm guessing it's just too capital intensive, too much R&D. I can't see current airliner makers investing until forced (Elon?). Certainly NOT Boeing. Maybe China?
Maybe the best one I've seen is
Home | Wright Electric who plan to fly converted BAE 146 with Aluminium Air Battery/Fuel Cell in 2026, maybe for EasyJet (promo material/wikipedia not clear). Aluminium has to recycled at a smelter - so a cartridge system (maybe pellets) would be used.
Aluminium Air Chemisty | metalectrique people have got to 1350 Wh/kg (maybe more now), Wright expect to get to 2000 Wh/kg.
I've no idea of economics but this does seem like an avenue to pursue. Any more info appreciated.