The COVID-19 pandemic has drastically affected airlines. Now, in an effort to woo travelers back to the skies, airlines are adopting more flyer-friendly policies. United Airlines led the way by announcing the elimination of change fees and standby fees. Within 24 hours, Delta Air Lines announced a similar policy and American Airlines went even further in its policy changes.

These changes may leave you reassessing which airline is best for you. So we dug into the details of the policies of the four major U.S. airlines. Here are the pros and cons of each to help you determine which airline to fly.

When should you fly Southwest?

Southwest Airlines has long been known — and beloved — for its lack of fees. And even after American, Delta and United made drastic policy changes this summer, Southwest remains the most flexible airline.

Southwest passengers can still change or cancel a flight up to 10 minutes before departure, regardless of destination. That policy bests Delta and United, both of which allow changes only to flights within the U.S. and to Puerto Rico and the U.S. Virgin Islands.

Unlike the three legacy U.S. airlines, Southwest doesn’t offer basic economy. So you don’t have to pay more for a ticket that allows changes.

Plus, Southwest famously still lets all passengers check two bags for free. That’s a trump card for Southwest when you’re traveling with checked bags.

Even better, Southwest has committed to having “middle seats open” through at least Oct. 31, 2020. True to form, Southwest is doing this a little differently: With its open seating policy, Southwest is creating more space onboard by capping the number of passengers who can book a particular flight. But you can still sit in a middle seat if you want.

When should you fly American?

Under the new policy, there are no change fees on flights to any of the 50 U.S. states, Canada, Mexico, the Caribbean, Puerto Rico or the U.S. Virgin Islands — as long as you don’t book basic economy. Neither Delta nor United include flights to Canada, Mexico or most of the Caribbean in their new policies. This makes American (or Southwest) the go-to for booking flights to these regions.

Even better, American will give you a voucher for the price difference if you change to a cheaper flight. For example, say you change from a $500 flight to a $300 flight. You’ll get a $200 voucher toward future travel. This is similar to Southwest’s change fee policy. United has clearly stated that passengers won’t get the fare difference, and Delta hasn’t yet ironed out the details of its policy.

That means American and Southwest will be the best options when you’re booking an expensive flight. If the fare drops, you can make a free change to the cheaper option and retain a voucher for the difference.

In addition, starting Oct. 1, 2020, all American Airlines passengers will be able to standby for free. That’s regardless of the type of ticket you buy or the route you’re flying. The only limitation is that you have to fly to the same destination.

This new standby policy matches United’s new policy, which doesn’t go into effect until Jan. 1, 2021. Not even Southwest allows that kind of flexibility on its cheapest Wanna Get Away fares. So American and United would be your best choices if you’re flying a route with multiple daily flights and want the option to take a different flight.

Though American’s new policies lead the way, there are other considerations to keep in mind. Unlike Delta, Southwest, Alaska and others, American is booking flights completely full. So you may want to opt for another airline to lower your infection risk when traveling during the pandemic.

American Airlines basic economy

American Airlines used to have some of the most restrictive basic economy policies. Now, American has some of the best. Basic economy passengers can already bring a full-size carry-on bag on board and purchase seats at the time of booking. Starting Oct. 1, 2020, American will also let basic economy passengers add perks like upgrades, priority boarding, extra-legroom seats and even flight changes on the day of departure.

However, passengers can only make free changes or cancellations to basic economy tickets purchased by Dec. 31, 2020. After that, American’s basic economy fares return to being nonchangeable and noncancelable.

When should you fly Delta?

Delta was quick to match United’s new change fee policy, adopting the same general policies for the same regions. Effective immediately, Delta won’t charge a fee for you to change a flight within the U.S., Puerto Rico or U.S. Virgin Islands. As with American and United, basic economy fares aren’t eligible to be changed.

While Delta claims it has been working on these changes since 2019, its policy leaves unanswered questions. For example, a Delta spokesperson told NerdWallet that the airline is still finalizing details of its policy, including whether to provide a voucher for the fare difference if a passenger changes to a cheaper flight. So you’ll want to stick to American or Southwest if you’re hoping to retain a credit for changing to a cheaper flight.

However, there’s one way Delta clearly beats both United and American: blocking middle seats. Delta has committed to blocking middle seats on flights through at least Jan. 6, 2021. This helped land Delta at the top of NerdWallet rankings of the airlines that have handled COVID-19 the best.

Delta basic economy

Delta was the first U.S. airline to introduce basic economy fares back in 2012. Basic economy passengers can bring a full-size carry-on bag on board, but you won’t be able to select your seat before check-in and elite members won’t get upgraded.

Normally, Delta basic economy fares are nonchangeable and noncancelable. However, Delta is allowing changes to all Delta basic economy tickets purchased by Dec. 31, 2020. That’s the same policy that both American and United have adopted.

When should you fly United?

That leaves United as the last — and least, in this case — of the four major U.S. airlines. United gets a lot of credit for being the first airline to eliminate change fees and standby fees. However, its change fee policies were quickly matched by Delta and then beaten by American.

Starting Jan. 1, 2021, all United passengers can stand by for an earlier flight for free. American matched this policy but is launching it on Oct. 1, 2020.

Like American, United is continuing to book flights to capacity during the pandemic. In NerdWallet’s rating of how airlines are handling COVID-19, United tied for fourth behind Delta, Alaska and Southwest — beating only American and Hawaiian.

Of course, United may be the only airline to operate a nonstop flight on your route, particularly after the carrier added new nonstop routes this fall. By flying direct, you can limit your time aboard the aircraft and in airports, which may be a good reason to choose United under certain circumstances.

United basic economy

As with the other legacy airlines, United is allowing changes to all basic economy tickets purchased by Dec. 31, 2020. However, after that, United basic economy tickets won’t be changeable or cancelable.

The bottom line

If you have a choice, pick the airline with the most flexible and generous change policies. Two airlines really stand out: Southwest and American. Southwest is long known for having no change fees and allowing two free checked bags. Plus, Southwest hasn’t introduced a stripped-down basic economy fare. Meanwhile, American has adopted the broadest and most generous change fee and standby fee policies of the three legacy airlines.

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