Traveling solo can result in higher ticket prices, study finds

• A new study found solo travelers on major airlines pay more than individuals in a group. The higher fares were found on Delta, United, and American Airlines. They have since been removed from Delta and United.

Airlines change ticket prices all the time, which can be a tremendous source of stress and frustration for flyers. But a new study has found yet another headache for people who are traveling without a friend or loved one: They could be charged considerably more for the same seat.

Thrifty Traveler turned a lot of heads recently after one of its editors noticed the price for a solo ticket was more than $50 higher than the per-ticket price for the same seat when buying two. That led the site to study hundreds of fares from multiple carriers. The report, published last Thursday, found Delta, American and United were all charging more for solo flyers—sometimes by a very significant amount. One flight saw a $266 difference between solo and multiple passengers, meaning solo travelers would pay nearly twice as much as people in a group.

Delta and United have both since rolled back the practice and are now charging the same for solo and group tickets, the website reports.

It’s unclear how long the practice has been going on—and also unclear if the rollback is permanent or temporary.

Delta, United, and American all did not immediately respond to Fortune‘s request for comment.

The study found the divergent fares weren’t universal. “You won’t see it on each and every route,” Thrifty Traveler wrote.

Dynamic pricing has long been a standard practice for airlines. Fares go up and down in real-time, using historic booking data as a guide. Business travelers, who are the bread and butter of airline revenues, tend to travel solo, so one theory is airlines are looking to increase their revenues from those travelers.

Airlines are already seeing a drop-off on international travel this year, especially visitors from Canada, as tensions between the U.S. and its neighbor to the north increase.

This story was originally featured on Fortune.com