Perhaps it's worth comparing to people in wheelchairs. Airlines accommodate a few wheelchair-bound people on flights, but if more than that number want to fly, they need to pay extra. Shit luck for them, but the alternative would be for everyone else to subsidise wheelchair-bound people whenever they want to fly. If you consider, for the purpose of this conversation, being tall as similar to being wheelchair-bound that's the choice.

So what happens with people of below average intelligence and physical ability? They're likely to suffer from lower earnings. Should a person of average height and on minimum wage subsidise a well-paid tall person?

In an ideal world, chairs would adjust so that everyone is comfortable and still allow the same number of people on the plane at the same price. However, in the real world, we probably have to accept that allocating comfort based on ability to pay, with a bit of flexibility on both sides, is the best outcome.