Originally Posted by fzwinter
This is known as "hidden-city" ticketing and is a big NO-NO among the airlines. You run the risk of being charged a much higher fare and losing your miles from the trip and maybe even your entire FF account. Don't do it!!
This also wouldn't work if you had checked luggage as it would have to be checked all the way through.
fzwinter is right...this is hidden city ticketing, but people do disembark at intermediate points to save money. As long as you don't make it a habit it shouldn't be that big of a deal. I'd suggest telling the GA that something came up in LA that required you to stay, this way the plane isn't held up for you.