Let's not spread fallacies here - Delta CAN NOT charge you retro-actively for a fare they feel is in line with what you flew. They claim they will threaten to do so - but there is no law to back this up nor a court who would approve such a claim. In the eyes of the law - when you purchase a ticket, you are purchasing it to point A to point B; however if the airline should chose to route you through another city - they do so at the risk of knowing that a passenger may willingly choose to get off at that point, with no monetary reprecussions other than denying that passenger frequent flier miles. The real issue at hand is that the airline would have to prove that they lost money in actual expenses (not *potential* fare sales) due to this passengers behavior - and the reality is, the airline saves money whenever one does this (as they have an empty seat on another flight which can either garner additional revenue or go empty but wouldl ultimately mean less fuel/services would be used as a result).