Anyone who flies American, Alaska, or United can earn major bonus miles at Apple right now, but the deal only lasts 24 hours

• Shopping portals offer an easy way to earn miles, points, or cash back on purchases you make online.
• Travel brands from American Airlines to Chase to Marriott run these portals, and you simply have to log in to your loyalty program account, search for a retailer through the portal, then click through to make your purchase.
• While some retailers routinely have high shopping portal bonuses, it's pretty rare to find a high earning rate for Apple.
• On Monday, December 9, earn 10 American miles per dollar, or 8 miles per dollar with Alaska or United on Apple purchases, compared to the usual rate of 1 mile per dollar.
• Consider using a credit card like the Chase Freedom Unlimited (to maximize your points earnings) or the Platinum Card® from American Express (to get purchase protection) to make your purchase.
• Read more personal finance coverage.

If you're looking to buy AirPods, an iPhone, or any other gadget from Apple, Monday, December 9 is the time to do it. You can currently earn 8 to 10 miles per dollar on Apple purchases made through the American Airlines, Alaska Airlines, and United Airlines shopping portals. American is offering 10 miles per dollar, while Alaska and United are offering 8x miles.

This elevated earning rate is only available on Monday, though these shopping portals have been known to offer 8x to 10x miles at Apple several times a year.

Shopping portals are a great way to maximize your online purchases by earning extra points, miles, or cash back on every dollar you spend. Most airlines - along with banks like Chase, a handful of hotel brands and cash-back sites like Rakuten - run these portals, and you simply have to be a loyalty program member to use them.

For example, United's shopping portal is called MileagePlus Shopping. To earn miles through it, you need to log in to the portal using your United MileagePlus loyalty program account credentials (or create one for free), navigate to the retailer you want to shop with, then click through to make a purchase.

So, in this case, you'd find the store listing for Apple, then click on the "Shop now" button. Just make sure you make your purchase in this same window; the portal awards you extra miles by using cookies to track your purchase, so if you click out of the original tab you used to navigate through the portal, you won't get those rewards.

Travel website The Points Guy values American miles at 1.4 cents apiece, so earning 10 miles per dollar would get you an 14% return on your spending. TPG values United miles at 1.3 cents apiece, so earning 8 United miles per dollar would get you a 10.4% return.

Other shopping portals offering bonus miles on Apple

In addition to Alaska, American, and United, the following airlines are offering elevated bonuses for Apple purchases today only:

• Delta SkyMiles: 6 miles per dollar
• Southwest Rapid Rewards: 4 points per dollar

The best option for you will likely depend on which program you have the most miles with. If you already have tens of thousands banked with United and zero with American, for example, it probably makes more sense to go through United's portal even though it's offering fewer miles per dollar. That way, your new miles will get you closer to your next award instead of starting your earning from scratch.

Which credit card to use

What makes shopping portals extra lucrative is that the points, miles, or cash back you earn through them are in addition to what you'll earn from the purchase with your credit card. So using a credit card that earns you bonus points is a great way to stack your earnings.

Most credit cards don't offer bonus rewards on purchases from big-box stores, but the Chase Freedom Unlimited could be a good option thanks to its earning rate of 1.5% cash back on all purchases. That becomes even more rewarding if you also have the Chase Sapphire Preferred Card, Chase Sapphire Reserve, or Ink Business Preferred Credit Card, because then you can combine your cash-back rewards with full Ultimate Rewards points and ultimately transfer points from the Freedom Unlimited to travel partners - including, incidentally, United.

Another good option would be a credit card that offers purchase protection, since Apple items are costly and you'll want to make sure your tech is protected. The Platinum Card from American Express is a top rewards credit card for many reasons, but a lesser-known one is up to $10,000 for covered incidents of loss, theft, or damage for up to 120 days from your date of purchase. See the benefit terms for more info.

Click here to learn more about the Platinum Card from American Express.

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Please note: While the offers mentioned above are accurate at the time of publication, they're subject to change at any time and may have changed, or may no longer be available.