Delta Air Lines (DAL -0.26%) said Monday it will continue to block middle seats through the end of April, as the airline tries to differentiate itself among customers nervous about flying during the pandemic.

Most airlines took steps to ensure space between passengers in the early days of the pandemic, but Delta is the only one to continue the practice into the spring. Alaska Air Group, one of the last holdouts, switched to offering a "premium" class ticket for rows without middle seats but opened up the rest of its cabin at the end of January.

A Delta plane unloading on the tarmac.

Image source: Delta Air Lines.

The move is a risky one. Airlines including Delta are losing billions right now, and forgoing potential revenue could mean pushing back Delta's goal to hit cash-flow breakeven in the months to come. Delta appears to be wagering that the added sense of security can help feed demand for the seats it is making available, and over the long term help establish the airline as a premium operator.

"We want our customers to have complete confidence when traveling with Delta, and they continue to tell us that more space provides more peace of mind," Bill Lentsch, the company's chief customer experience officer, said in a statement. "We'll continue to reassess seat blocking in relation to case transmission and vaccination rates, while bringing back products and services in ways that instill trust in the health and safety of everyone on board -- that will always be Delta's priority."

The airlines are hopeful that as the COVID vaccine rollout continues, they will see an uptick in demand for summer vacation travel. Delta did not indicate whether this extension until the end of April would be the last one for the middle seat policy, though CEO Ed Bastian has said he expects the policy to end in the first half of 2021.