While missing a single connecting flight due to an emergency or a genuine delay won't result in a ban, intentionally doing so as part of a strategy known as "hidden city ticketing" can lead to severe consequences. Hidden city ticketing is when a traveler books a flight with a layover in their actual destination because it is cheaper than a direct flight, and then simply walks away at the connection. Airlines consider this a violation of their Contract of Carriage. If a passenger is caught doing this repeatedly, the airline may take several actions: they can void the remainder of the ticket, freeze or delete the traveler's frequent flyer account and all accrued miles, or even bill the traveler for the difference in fare. In extreme cases of habitual abuse, an airline can indeed blackball or "ban" a passenger from future travel on their metal. Furthermore, when you miss a segment of an itinerary, the airline's system almost always automatically cancels all subsequent legs of that journey, including the return flight, which can leave a traveler stranded without recourse or refund.