Likewise, if you want them to be, so is public transport.
Though, here's a question: I don't think I've ever seen planes classified as public transport — is that just my observations being weird, or is that a true distinction? And if genuine, why?
The fact that long-distance highways tend to be free speaks more to politics than logic, and there are a few notable exceptions (eg Japan) where all expressways are tolled.
And in Switzerland for example you just pay a really high gas tax that funds the highway, plus you have to pay a one time fee and get a sticker, otherwise you are not allowed to drive on the highway.
I think using the train is more like using the car. I can agree that the tracks are a public good, but actually using the train is clearly different from that. Just like the government provides me roads, but not with rides.
> I don't think I've ever seen planes classified as public transport I guess my framework fits that, because while you may need to maintain the air and the airport, the individual flights only help the individual person.
In remote parts of the world, planes absolutely should be classified as public transport. Remote towns in Alaska, for example, are essentially inaccessible without bush planes.
However, planes are expensive to operate on a per-passenger basis, and in most places there are cheaper ways to facilitate helping people move around, especially since most trips from most people are short-distance.