Buses and planes are both great! Both have advantages and disadvantages, and different cost structures. I trust people to make their own decisions about trade-offs for travel that work for them and their situation. When we arbitrarily pick one and shovel free money, land or infrastructure toward it, we are putting a thumb on the scale and depriving people of the power to make their own decisions.

Of course, we can argue that there are network effects or natural monopoly effects for fixed infrastructure like roads and rails, and thus there must be a public role. However policy rarely seems to remain at this reasonable position and instead quickly expands into something altogether different.