Airline change fees may be a thing of the past, but not all rules are the same; know your options before you book.

You can cancel a flight within 24 hours of booking, thanks to this Department of Transportation rule. After that, all airlines—with the exception of Southwest, which charges only the fare difference—charge a fee to change your reservation…that is, until now.

Starting late this summer, most major U.S. airlines eliminated change fees to accommodate the unpredictable effect COVID-19 has on travel. Each airline’s policy, however, is slightly different. (Note: If you change a reservation, you still have to pay the difference between the old fare and new one, if any. If the new fare is less than your original, you don’t get a refund.)

Here’s a summary of the new rules:

Alaska Airlines

On September 1, Alaska Airlines eliminated change fees on all previously-booked domestic and international tickets except Saver fares. All new tickets, including Saver fares, may be changed without fee through December 31, 2020.

Alaska also allows certain tickets to fly standby for free, including refundable main cabin tickets and first class tickets.

Allegiant Air

Allegiant “Trip Flex” bookings can be cancelled up to one hour before a flight. Otherwise, the airline charges a $75 change fee per segment, plus the difference in airfare; changes or cancellations must be made at least seven days before a scheduled departure.

American Airlines

American Airlines eliminated change fees on August 31 for all previously-purchased domestic and short-haul international flights, including those to and from Canada, Mexico, and the Caribbean, plus Puerto Rico and the U.S. Virgin Islands. This applies to premium cabin fares and most main cabin tickets (but not Basic Economy).

Starting October 1, flying same-day standby is now free for all domestic and international flights, no matter the type of ticket. The airline is also waiving change fees on all tickets, including Basic Economy, purchased by September 30, 2020, for travel through December 31, 2020.

Delta Air Lines

On August 31, Delta eliminated change fees for travel within U.S. states, Puerto Rico, and the U.S. Virgin Islands for all tickets except basic economy. Delta also offers same-day standby for $75; again, Basic Economy tickets are not eligible.

For newly-purchased, flights, Delta has waived change fees for all domestic and international tickets—including Basic Economy—through the end of the year.

Frontier Airlines

Frontier bookings made between

-March 10 and April 15, 2020,

-July 2, 2020 and July 31, 2020, and

-August 31, 2020 and September 30, 2020

are permitted a one-time change without a fee; the change must be made seven or more days prior to departure.

Hawaiian Airlines

Hawaiian Airlines eliminated change fees on September 3 for flights between Hawaii and the U.S. mainland, international destinations, or within the Hawaiian Islands for Main Cabin, Extra Comfort or First/Premium Cabin Class bookings. Main Cabin Basic fares are included in the new policy through the end of the year.

The airline also offers same-day standby tickets to qualifying Pualani Platinum members, Pualani Gold members, and corporate customers who booked through the Corporate Web Portal.

JetBlue

JetBlue is waiving change and cancellation fees for bookings made through February 28, 2021.

Southwest Airlines

Southwest does not charge a fee to change any fight.

Spirit Airlines

Spirit is waiving change and cancellation fees for tickets booked by September 30.

United Airlines

United Airlines eliminated change fees for standard economy and premium tickets within the U.S., Mexico, and the Caribbean. United also waived change fees for all tickets (including Basic Economy) issued before December 31 for both domestic and international travel.

Starting January 1, 2021, United will make flying same-day standby free for all customers. Currently, MileagePlus members can make same-day changes for $75, and Premier Gold, Premier Platinum, and Premier 1K members can do so for free.

Twist’s Take: Airline no-change-fee policies are not the same; know before you go.