Q. I have read your recent posts about shopping through airline websites and registering your credit cards to get bonus frequent flyer miles. That is brilliant! But, here is my question: If you use a credit card that gives you frequent flyer miles, do you get the miles on your credit card, and on the airlines that you choose? And, what if you registered your cards on, say, three different airlines. Would you get frequent flyer miles on your credit card and all three of the airlines simultaneously (assuming they all are participants in that particular store)?

A. The reader is referring to an article I wrote and tweeted about warning people that if they're going to shop online it's foolish not to do so through the airlines' shopping mall sites. For those who missed it, airlines award bonus frequent flyer miles (in addition to any miles awarded by using an airline-affiliated credit card) when you shop at over 300 online merchants. Same prices, same stores, same merchandise—the only difference if that if you buy an Apple iMac, for example, at Apple.com you only get miles from your credit card; but if you buy it on Apple's website by first going through an airline shopping mall, you might get an addition one to four miles per dollar spent. These are the same merchants you already shop at: Macy's, Sears, Target, Wal-Mart, Gap, Barnes and Noble, AT&T Wireless, Netflix, the iTunes Store—the list goes on and on.

Now to the question: yes, you do get the bonus miles in addition to miles earned by using your credit card. But no, you can only get miles on one airline at a time per purchase. Click here to see links to all the airlines' shopping malls.