Ever wondered about frequent flyer programs? These programs, created as a way to ensure customer loyalty, have since allowed travelers to fly around the world for very little money. You can earn airline miles in various ways, including through credit card welcome offers, air travel, spending on co-branded credit cards and more.

But at the end of the day, what are these miles actually worth? Below, we examine the value of each airline’s award miles and its valuation of 40,000 miles.

Airline miles to dollars: An overview

Based on NerdWallet’s most recent analysis, here’s how 40,000 miles shakes out in dollar values across major U.S. airlines. You should expect 40,000 miles to be worth about $516.

Here, we’ll look closer at each airline — highlighting sweet spots where you could get even more value per point or mile than on average. Tip: You can use NerdWallet’s free calculator to determine if you should book a flight with points or miles.

Feel free to jump ahead to your airline of choice:

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Alaska Airlines.

American Airlines.

Delta Air Lines.

Frontier Airlines.

Hawaiian Airlines.

JetBlue Airways.

Southwest Airlines.

Spirit Airlines.

United Airlines.

40K miles value, broken down by airline

Alaska Airlines: $560

Although it isn’t one of the big three U.S. airlines, Alaska Airlines operates a comprehensive route network with more than 115 total destinations. In addition, due to its membership in Oneworld and a strong group of individual partnerships, you’ll find your miles redeemable with plenty of airlines, including American Airlines, British Airways, Cathay Pacific, Icelandair and more.

The cost to redeem your Alaska miles will depend on your carrier; you’ll find different rates hinging on whether you’re flying Alaska or one of its partners. Overall, we value Alaska Mileage Plan miles at 1.4 cents each, which means 40,000 miles will be equal to $560 worth of travel.

When flying with Alaska Airlines, you’ll pay a range of pricing depending on demand, distance and fare class.

For example, you can fly nonstop from San Francisco to Orlando for 12,500 miles on a low-demand day.

You can also flip the same flight, paying just 12,500 miles to return from Orlando. At these rates, you would be able to take three one-way flights across the country for 37,500 miles — with 2,500 miles left over.

However, you may find better results when flying with some of Alaska’s partners. For example, consider this one-way flight from San Francisco to Fiji, which will cost you 40,000 miles.

Eleven hours is a long time to spend on a plane, but it’s an excellent deal when you consider that the cash price for this flight is over $800.