I always thought that the Captain of a Aircraft would have the same powers as the Captain of a merchant ship, and they were conciderable.
Because Merchant ships were concidered soverign territory of the country they were registered in,Ships Captains had almost diplomatic immunity and similar powers to a Govenor of a small state.
Used to be said that a Captain could do anything he wanted to you bar give you a baby, and some of them were likely to try even that.