Increasingly American Airlines has been imposing a new rule in its fares to make your tickets more expensive.
It used to be that if two one-way fares, say San Diego to Dallas and Dallas to Fort Lauderdale, were cheaper than the fare for San Diego to Fort Lauderdale you’d pay the cheaper ‘sum of the two one ways’ for your ticket. Now for many of the cheapest fares in many markets American has updated their fare rules to prohibit “End of End Ticketing” which means you cannot combine the cheap fares, you have to pay the more expensive fare.