Originally Posted by
Often1
The general misperception in hidden-city is that the carrier can require a pax to fly a segment. The carrier cannot. The sole issue at hand is, "what is the fare?" The fare from A-B is $100 and the fare from A-C is $75, it just so happens there is a connection at B. If you want to fly A-B, you pay $100 and if you want to fly A-C, you pay $75. If you buy an A-C ticket and decide to end at B, you owe $25. It's that simple.
No its not that simple. You could terminate at B for any number of valid reasons. If the airlines thought this was not the case then they would be charging those penalties left right and center. Let us see what they do charge for... seat selection, baggage, food (buy on board), change fees, pillows, blankets, headphones (phew I am surprised they haven't started charging for seat covers yet). Rest assured if the airlines really thought that they could squeeze out more revenue because you "owe" them for a flight that you had paid for but did not use then they would go after you to make you pay. It is just that simple.