At all? Often? If I fly once a year over a distance of over a thousand kilometers, is it fine or not?

What can I, and individual, do to fix the issue that it takes three trains with a high chance of failures and delays, to get to a destination within my country on what is a direct route from city to city?

etc.

Stop shifting blame to individuals

Or ban fossil fuel powered private jets, so the elite is incentivized to invest into development of hydrogen airplanes to the grand benefit of everyone. If they want something done it happens. It's up to the rest of us to force them to want it.