[maxwell22]

Tax payers. In Germany, airplane fuel is not taxed.

See this Greenpeace study (in German) about how much cheaper flying is than train rides and why:

https://www.tagesschau.de/inland/regional/nordrheinwestfalen....

[testrun]

Not taxed does not mean it is subsidized. Subsidy is when money is paid by the government to the airlines.

[somewhereoutth]

Tax on fuel reflects the externalities to the whole of society, and arguably it is not high enough.

So exempting tax (equivalently not charging for externalities) is indeed a subsidy, a transfer of wealth from government (and so society) to the airline operators.