Long-distance battery airplanes are literally impossible. If you don't agree with hydrogen powered aircraft, you are advocating for conventional airplanes forever.
I don't have a dog in this fight. I'm just explaining why hydrogen will never be popular. For a new technology to be adopted, it has to be better than the status quo. Compared to current aircraft, hydrogen costs more, has new safety concerns, and requires new infrastructure to transport and store the fuel. If that means aircraft will keep using fossil fuels, well then I guess we'll keep using fossil fuels.
I think hydrogen (or something made from it) and fuel cells will win in the medium term. It's energy inefficient, but we're going to have a lot of cheap energy which will make lots of energy inefficient things reasonable, as long as you can store the output in some way.
Having said that, with future automatiion, I do feel there's room for aircraft that combine and re-assemble themselves in mid air. For example, a VTOL tug that lifts off and starts a craft flying, but then detaches and returns to base.
This can potentially be repeated on the landing side, and even mid-air "re-fueling" via battery drones.
Possibly I just watched too many kids shows where vehicles did this and it's now my equivalent of the Jetson's flying cars.
Feels like the next crazy project for Silicon Valley Billionaires to look into now that electric flight, jetpacks, rockets that land vertically etc. are all solved problems.
The more interesting question is if it would not be a better course of action to build out high-speed rail to replace domestic air transit, and keep synth-fuel reserved exclusively for trans-oceanic flight.
Trains are a solved problem, Japan, China and France show how it's done. No need to wait for miracles or SV billionaires - ffs, Hyperloop was (likely) only created to disturb the planning of California's HSR [1]!
California high speed rail is still being built. Hyperloop didn't have any impact beyond getting some people to think, "Why is this so expensive?"
The CA HSR project was started in 2008, when voters passed Proposition 1A to provide $10 billion to fund high speed rail between SF and LA with a maximum travel time of 2 hours and 40 minutes. Initial estimates were that trains would be running by 2022 with the project completed by 2029 at a cost of $33 billion.[1] Construction started in 2015. Now the official projection is to have trains running between SF & LA in 2033 at a cost around $100 billion, though in reality the two cities will likely never be connected.[2]
High speed rail doesn't make much sense in most of the US. The country is so big that most routes would take significantly longer than aircraft, even counting the extra time spent in security and traveling to/from the airport.
If we're talking outside of flight, then I think jumbo jet sized hydrfoil electric cargo ships will be an interesting challenger to both cargo flights and to larger cargo vessels.
Trains are cool though. One big EU project currently is to connect up the train lines better across borders which are often still country centric in their network layout, which defaulted the medium distance capital to capital journeys to air transport.
Forever is a long time, but our grandchildren will still be taking long-haul flights on conventional aircraft powered by turbine engines burning kerosene (possibly synthetic). The advantages of liquid hydrocarbons over hydrogen fuel are overwhelming in terms of safety, handling, and aerodynamics.
