>Sleeper trains are held back by flying getting subsidised heavily by not having kerosene taxed

Is whatever fuel trains use taxed? If not, I don't see how this is relevant.

>and national governments giving airports effectively unlimited room to grow

Which countries are those? For instance in UK they wanted to expand Heathrow since as early as 2006, yet due to various government shenanigans isn't due to complete until 2040, assuming it doesn't get backtracked again.

https://en.wikipedia.org/wiki/Expansion_of_Heathrow_Airport

Moreover since you're comparing against trains, don't trains need land as well, for the tracks and stations? Why do trains seemingly get a free pass from you on that?

>Trains in general are held back by governments not investing in rail infrastructure, because the pork barrel of another motorway link is so hard to resist (and we're not properly maintaining these either).

What makes motorways more of a "pork barrel" than train tracks?