This story has been updated.

When the pandemic sent travel into a tailspin, airlines updated their formerly strict policies on canceling or changing flights to encourage customers to book with confidence. But as the number of passengers ticks up, some of those old practices are creeping back — especially for the cheapest flights.

For flights booked April 1 or later, some carriers are essentially reverting to pre-pandemic treatment of their least expensive fares. That means basic economy fares on American will again be “non-changeable and non-refundable.”

Low-cost carriers are also nearing the end of their extra-flexible days. Spirit said it is waiving change and cancellation fees for passengers who book by April 4. Frontier said that for bookings made after March 31, pre-pandemic policies will apply — which means no fee for changes made 60 or more days before departure, a $39 fee for changes between 7 and 59 days of a flight, and a $59 fee for changes closer to the date of a trip.

Several airlines extended flexibility at the last minute — some after this story originally published — giving customers extra time to make up their minds.

Delta and United had both been slated to reinstate restrictions on their basic economy tickets as of the end of March or beginning of April. Delta’s basic economy tickets were reverting to nonrefundable and non-changeable after March 30, and United’s were switching back to non-changeable after March 31.

But on Wednesday, both said they would continue to allow flexibility on those fares for another month, extending their waivers to allow changes to basic economy tickets through April 30.

On Thursday afternoon, Hawaiian Airlines said it also extended its waiver on changes for main-cabin basic fares through April 30. Those fares had been scheduled to revert to non-changeable at the beginning of the month.

And JetBlue said on Friday that it would allow no-fee changes to its lowest “Blue Basic” fare for tickets bought on or before May 31.

The airline had previously said that for flights booked on or after April 1, any changes to the lowest-fare tickets would come with a fee of at least $100. Before the pandemic, changes were not allowed to the fare at all.

“We know our Blue Basic customers need continued flexibility during these uncertain times,” the airline said in a statement.

Most airlines contacted by The Washington Post said they will work with passengers who are ill to make adjustments to their flights, even if they have booked non-changeable tickets.

Travelers who aren’t looking for rock-bottom prices can still benefit from the coronavirus-inspired changes. Major carriers have eliminated change fees for most fare categories on domestic and some international flights. Still, customers who are comparison shopping don’t always know they are booking the most restrictive tickets — and should be aware that for those tickets, changes will soon be impossible or costly.

Robert Mann, an airline analyst, said in an email that the reintroduction of change fees could be a deterrent to potential passengers.

“Airlines need advance bookings to generate working capital, and reimposing change fees will frustrate advance bookings by those who are on the fence, considering summer air travel, but uncertain about taking the risk of a nonrefundable booking with a possible stiff change fee,” he said.

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