> Being on the plane doesn't remove your right to free speech

While I agree with you that this was obviously a ridiculous overreaction, an air plane is not a public space. It's more akin to being in someones living room in that the pilot has absolute authority over whom to kick out for whatever reason. If they don't like your hair, they can have you escorted out by police if you don't comply. They won't do it normally because it's bad PR and their employer wouldn't like it, but they could. Not free speech amendment violated.