Blocking off middle seats on airplanes can significantly reduce the risk of COVID-19 exposure, according to a new study from the Centers for Disease Control and Prevention. At this point, however, nearly all major domestic airlines have stopped blocking middle seats.

We’ve all known for a while now that wearing masks and social distancing are two of the best ways to prevent COVID from spreading. Turns out the same is true on airlines. “Distancing can have a significant protective effect,” said James Bennett, a research engineer at the CDC who worked on the study.

Bennett explained just how much a difference it makes when airlines block middle seats varies.

“At the low end, we were looking at a 23% reduction in exposure, just from the fact of not being seated right next to another passenger if they happen to be infectious,” he said. At the high end, it’s a 57% reduction in exposure.

But, for airlines, at this point in the pandemic, “I don’t imagine this is gonna make a whole heck of a lot of difference,” said aviation analyst Richard Aboulafia. “The airlines have been really diligent at enforcing mandatory mask policies. It’s been a really effective tool.”

And, as vaccination rates rise, more and more people are feeling comfortable booking flights, Aboulafia said.