fine airlines for over-selling airline flights. Selling something you don't have is illegal in any other industry.

The airline industry continually oversells flights on a daily basis causing problems of many degree with airline travelers. In any other area this is considered fraudelent and illegal to sell something you cannot legally deliver. Some may say moving to a next flight is a reasonable resolution but the reality is then you are providng false advertising to your customer. Airlines charge for flights based on times and if a customer pays a premium price for a flight and it is oversold and they are booked on what is ultiamtely a cheaper flight it could be said that they have been defrauded and forced in to a more expensive flight even though the airline has not delivered. If there were penalties for airlines when they oversold a flight they would certainly be more cautious of this practice.