Every major U.S. airline has a loyalty program, and if you like, you can join them all. But rather than earning small quantities of miles spread over multiple rewards programs where they may never amount to an award flight, it makes sense to focus your spending and flying to one or two.

Choosing the best airline rewards program for you involves weighing a number of factors. Here’s how to evaluate some of the country’s biggest frequent flyer programs to decide which will be most rewarding for you.

The biggest U.S. frequent flyer programs

The loyalty programs of major U.S. airlines include:

Alaska Airlines Mileage Plan.

American Airlines AAdvantage.

Delta SkyMiles.

Southwest Rapid Rewards.

United MileagePlus.

All of these loyalty programs are free to join. We recommend opting in to their email marketing to learn about the latest specials and promotions.

With each of these loyalty programs, you'll earn miles by flying the airline or its partner airlines or by staying in partner hotels. Other ways to earn miles include making your purchases with a co-branded credit card and using the airline’s shopping and dining programs.

To choose from these major programs, consider the following questions.

What to consider when choosing a frequent flyer program

Do you live in a hub city?

Unfortunately, not every flight is a nonstop between your hometown and your preferred destination. Airlines typically pick cities around the U.S. to serve as hubs, which allows them to funnel connecting flights through strategically placed airports.

If you live in one of these cities, there’s a good chance your first choice will be an airline that has a hub there. Departing from a hub city, you have increased options for nonstop flights, saving you the time and hassle of connecting through another city.

For travelers who live in regions with multiple airports, you have more options. For example, in Southern California, there are five airports in driving distance from each other. The airports near you can factor into your decision when picking a frequent flyer program.

Where do you want to fly?

Think about the cities that you travel to frequently and your future travel plans. Just because an airline has a hub in your city doesn’t mean it is the right one for you. Search flights from your home airport to some of your future destinations to see which airline offers the lowest fares, most direct flights and multiple departure times.

Do you want to fly in premium cabins?

When picking an airline, make sure it offers the type of seats and experience that you have in mind. Southwest Airlines is popular, but its planes have economy class seats only. For first class seating and all of the perks that come with it, look to another airline.

How easy is it to earn miles?

When picking an airline to focus on, select one that makes it easiest for you to earn free flights.

Airline credit cards typically pay bonus miles when you buy tickets on that airline. Some also award additional miles when you make charges in select purchase categories. For example, the United℠ Explorer Card pays 2 miles per dollar spent on United flights, hotels and restaurants. If you spend a lot of money in these categories, the bonus miles can add up quickly. American, Delta, Southwest and Alaska also have co-branded credit cards that can accelerate your earnings.

Additionally, consider if the airline has transfer partners from other rewards programs. Transferred miles and points can speed your progress toward free flights. For example, American Airlines’ AAdvantage program lets you convert miles from Marriott, Hyatt and IHG hotels into airline miles. Chase Ultimate Rewards® points transfer on a 1:1 basis to United, giving you more options to earn miles.

How easy is it to redeem miles for flights?

For some people, earning airline miles is easier than redeeming them. Review the airline’s restrictions and fees on redeeming miles for flights.

Most airlines have eliminated blackout dates for booking award flights. In place of these restrictions, however, the number of miles to book flights during holidays or other popular travel periods increases significantly.

A mid-November flight from Los Angeles to New York City on Delta might cost around 6,500 SkyMiles. But the same flight over Christmas can range from 16,000 to 36,500 Delta SkyMiles, depending on the departure date.

Are there fees to check bags?

Travelers can pay up to $35 per checked bag each way. If you're traveling with family, this extra expense can add up. You can avoid checked bag fees by earning elite status or by buying your flight with certain co-branded airline credit cards. Or you can choose an airline like Southwest that gives every passenger two free checked bags.

Some travelers balk at paying the annual fees that typically come with airline credit cards. But if you're a frequent traveler, the money you save on checked bag fees can outweigh the cost of the credit card.

The bottom line

When choosing the best airline rewards program, take into account where you live, where you want to fly and how you want to fly. Also factor in how easy or difficult it is to earn miles and redeem them for a flight. Finally, make sure that the airline won't nickel and dime you with fees for checked bags, booking flights and other costs.

No matter which airline loyalty program you choose, getting the airline's co-branded credit card can make a difference in your earning power. Most offer a welcome bonus of tens of thousands of miles, which you earn after charging a certain dollar amount to the card in a specific time. These cards also pay additional miles on your purchases, and some come with other perks that help you save money and enjoy your travels even more.