Flying and sustainability
https://www.bbc.com/future/article/20210401-the-worlds-first-commercial-hydrogen-plane
not a technical article but gives an overview of some current developments, aspects, and parties,
My own impression at this stage in general is, that the gap between what one would like and what is possible is still there, multiple basic technical solutions are there (I have not seen really new ones yet... some discussions of the 1940s and 50s are refreshed though) , but the way we calculate in overall environmental terms and the combination of that with economic/enjoyment and financial and fiscal terms is still behind, that is a big risk overall.
To compare and select solutions, we need a bigger matrix than we have today, and that matrix is only partially clear... a bit like matter and dark matter;-)
Would be interesting to have someone come up with something completely new that shakes up developments.