Delta Air Lines, the last US airline still blocking middle seats, will end that policy in May as air travel recovers and more people become vaccinated against COVID-19. The decision announced Wednesday reversed a policy that had been in place since last April, and which Delta’s CEO had repeatedly cited as raising trust in the airline.

CEO Ed Bastian said Wednesday that nearly 65% of people who flew on Delta last year expect to have at least one dose of the new vaccines by May 1. That, he said, gave Delta the assurance to end seating limits.

The airline industry was divided over the utility of blocking middle seats to reduce the risk of spreading COVID-19 on a flight. Airlines including Delta, Southwest, Alaska and JetBlue limited seating for months, while United Airlines never did and American did so only briefly.

Social-distancing is hard if not impossible on an airplane, even with middle seats empty- a point that United CEO Scott Kirby made many times to explain his airline’s resistance to seat-blocking.

All the airlines mounted an aggressive campaign to reassure travellers about the safety of flights as long as everyone wears a mask – that’s now a federal requirement. They paid for a Harvard University report that concluded the risk of spreading the virus during a flight is low in part because of strong ventilation and high-grade air filters on most planes.

Air travel in the United States is recovering from pandemic lows. More than 1 million travellers have gone through US airports for each of the last 20 days, although March traffic remains down nearly half from the same month in 2019.

The numbers are rising heading into the crucial summer vacation season. Last summer was a catastrophe for the airlines, contributing to Delta’s full-year loss of more than $12 billion. The airlines are eager to boost revenue as quickly as possible, and that means selling more seats.

Delta announced a number of other changes. Tickets bought or expiring this year will be good through the end of 2022, Delta will offer a quicker path to elite status in its loyalty program for the rest of 2021, and it will bring back snacks on April 14.