Frontier Airlines aircraft.

Robert Alexander | Getty Images

Frontier Airlines said on Friday that it would require its employees to get vaccinated against Covid-19 or to show negative tests on a regular basis.

The low-cost airline’s announcement came hours after United Airlines said all 67,000 U.S. employees must provide proof of vaccination no later than October 25.

“As we continue to watch the rapid rise in new COVID-19 cases in the United States caused by the Delta variant, I am concerned for the well-being of our team members, their families and friends,” said Barry Biffle, CEO of Frontier in a press release.

Frontier said the majority of the airline’s employees were already vaccinated.

The Denver-based airline blamed the Delta variant on a drop in bookings last week, which led it to lower its forecast for the third quarter.