In addition to making frequent flyer miles harder to spend, airlines are expiring miles, if there's no activity in your account, faster than ever.

But one easy and painless way to make sure there's activity in your account is to do some online shopping using the airlines' "shopping malls." Even if you merely buy a 99-cent iTune you'll keep your miles safe for at least another year. And in addition, if you're buying a big ticket item, such as a computer, you can add some serious miles to your account.

For example if United offers an extra mile for every dollar spent with the Apple Store, one of their shopping partners and you buy a $2500 iMac computer, you get 2500 miles. That's a huge bonus. And there are often bonus offers on top of the bonus miles. United might offer an additional 2,000 miles if you spend over a certain amount.

Generally, these online shopping partners offer at least one mile per dollar spent, but sometimes they award 10 miles or more. And if you use your airline affiliated credit card, you get an extra mile, but the credit card miles pale in comparison to the shopping miles you can earn.

Scores of well known retailers participate in these airline malls, including Crate and Barrel, Best Buy, The Container Store, Dell Computer, Drugstore.com, Sears, Target, and Walmart, to name but a few.

Keep in mind that although the airline shopping sites listed below work with many of the same retailers, American might be offering 4 miles with a particular retailer while Delta could be offering just half that, so you've got to shop around while you're shopping around.

Links to airline shopping malls:

American

British Airways

Delta (Delta SkyMiles, for now, no longer expire, but you can still earn miles this way)

Hawaiian Airlines

JetBlue (miles don't expire but you can still earn miles)

Southwest Airlines

United

US Airways

Virgin America

Above image via Shutterstock

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