Southwest Airlines is lowering expectations for its third quarter as the delta variant spreads rapidly across the United States.

In a regulatory filing Wednesday, CNN says Southwest Airlines reported fewer customers are booking flights. The airline is also reporting an uptick in cancelations, according to CNN.

Southwest blames the delta variant for the drop in demand, CNBC reports.

The Dallas-based airline reportedly said July was profitable, but it expects turning profits in the third quarter will be more difficult.

CNN reports that the airline expects September revenue to be down by as much as 25% when compared to the same month in 2010

Southwest isn’t the only airline concerned about profits. Frontier said last week, best-case scenario, it would break even in for the second quarter, CNBC reports.

Some airlines are taking measures to make customers and workers feel safe.

United announced it would require all employees to be vaccinated against COVID-19 by the fall. Frontier customers are also required to be vaccinated or submit to regular COIVD-19 testing, according to Insider. Southwest does not have a vaccine mandate.