This is a Sabre problem and am still not sure if this is a software glitch or something in the way the tapes are loaded into the system. All of the fare rules that require a Saturday night stay state that the saturday night stay is based upon time of depature at orgin. So it is legal to fly out on Saturday night and return that Sunday even though you have "just arrived". The people at Sabre recognize this as a problem but due to the very small number of people who do this type of routing, they are taking their time to fix it.

The other problem is with the people at AA--they are not allowed to override what the system tells them so they come up with all sorts of excuses why these routings are not legal. I had someone tell me that it was a customs violation (huh) and another person called the Tarrif department and came back with some other lame excuse--when I tried to argue that the rule states "time at orgin", I was told "I work with this system every single day and it is obvious that I do not know what I am taling about".

The only way around this is to:
1)Book your travel on a non sabre based system.
2)Have a travel agent book it for you--they can override the system and price it out at the correct fare. Make sure you have a decent travel agent who understands these things.
or
3)Call American and try to explain to them what is going on. One good way to defeat their logical response to the lack of a Saturday night stay (since you are arriving on a Sunday) is to have them price it out for returning on Monday. That fare should be just as high since the Saturday night stay has still not been met. When it prices out at the lower fare, ask them why becuase you still do not have met the Sat night stary-- it tends to make them at least think about it. You can also ask them to make sure the system is listing the the London connection as a stopover. Once in awhile you will get someone in Tarrifs who understands the problem and is willing to override the system but most of the time you get people who either do not want to help you, are unable to help you and just don't care.

If you have any more questions or need more advie please let me know.