american, twa, and united programs are administered by the dining-a-la-card company. they keep track of which credit card you use for each program, so you cannot use the same credit card for more than one of those airline's programs.

continental & usairways uses transmedia as their dining sponsor. they give you a transmedia card tied to one of your credit cards; so once again, you cannot get credit for more than one program per meal.

the one way to get points on more than one airline is to use one of the above programs in conjunction with delta's skymiles dining. delta is all alone with their program, so if you can find a restaurant that is participating in both delta and (dining-a-la-card OR transmedia), pay for the meal with your credit card/transmedia card and present your delta skymiles card.

this isn't as easy as it sounds, though, since delta only has about 1,000 restaurants participating nationwide, and the other programs have over 6,000.