Budget-minded travelers have two strong incentives for booking summer travel now, before April rolls around: flexibility and cost.

At the end of March, major airlines will roll back the freedom to change tickets purchased at the basic economy rate. Those fares offer the lowest available price but deny the usual niceties such as choosing a seat at the time of booking.

Basic economy tickets booked by March 30 at Delta or March 31 at United or American will be changeable and incur no change fee, carrying on a pandemic-inspired benefit that had given reluctant fliers a safety net. After those dates, fliers holding basic economy tickets will need to use those tickets as booked or lose them.

That powerful incentive is coupled with another: At the moment, prices for summer flights remain low, but that could change in the next few weeks as travelers get vaccinated and book flights.

"We're seeing really, really remarkably cheap flights right now," said Scott Keyes, founder of airfare deal website Scott's Cheap Flights. He recently found round-trip airfares from Minneapolis-St. Paul International Airport to Las Vegas for $77 and to Hawaii for $336.

Summer has historically been one of the most expensive times of the year to travel, given the swell of travelers, from families free of school to people whose offices lighten the workload.

"A lot of folks, by dint of their schedule, are trying to buttonhole their travels into the few months of summer. With that rise in demand comes higher fares," he said. This year, that usual uptick could be compounded by a pent-up demand for travel.

Everyone hoping to fly this summer should be looking for good fares right now, but especially people seeking basic economy fares as all airlines look to restrict those tickets, said Kyle Potter, editor at flight deal and travel education website Thrifty Traveler.

Airlines started waiving no-change fees a year ago after the global pandemic kept people at home and off planes. By summer, they were announcing plans to keep the policy in place permanently for all but basic economy fares. Southwest Airlines, which has three levels of service including a bare-bones option, has never charged change fees for any of them.

According to Potter, it had always been clear that the days of free-for-all changes no matter what ticket you bought would end once travel rebounded. That day seems to have arrived. Delta told attendees of the J.P. Morgan Industrials Conference on March 15 that its March revenue is 40% higher than February's, and that people are booking travel more than 2 months out, rather than the few weeks or even days that had been standard during the heart of the pandemic, Potter said.

Keyes said he was surprised when airlines promised to eliminate change fees permanently for all tickets except those purchased at basic economy, a sign that they were pivoting to leisure instead of business travelers. The idea that once booked, fliers were locked in, had been a backbone of the ticketing model, he said. The fact that airlines were willing to upend their business model suggests the radical changes caused by the pandemic.

"Change fees had been a billion-dollar industry for the airlines," Potter said.

Potter noted that anyone who sees an airfare price they like should book it as soon as possible. "You'll get more bang for your buck now than you will in even potentially two weeks from today."

But after April 1, he said, fliers should consider skipping basic economy tickets.

"I definitely recommend that people give a long, hard look at paying for a main cabin fare for that certainty of changing your flights." Fliers also benefit from the ability to select a seat and tote a carry-on bag, which United and, soon, JetBlue limit.

But the best bet is to book now. As Keyes notes, you get a win-win. "You have cheap flights and the flexibility to change your flights later. That means you can book flights in pencil rather than pen."