United Airlines is cutting its schedule to deal with an increase in sickness calls among employees, CEO Scott Kirby told employees.

U.S. airlines have canceled thousands of flights over the holiday season through early this year due to Covid infections among crews and a series of winter storms. United first cut some flights before Christmas.

JetBlue Airways was the first carrier to cut its January schedule due to an increase in infection rates among crews, which was later followed by Alaska Airlines. American Airlines said it will do the same this week as Covid rates rise among regional carriers.

The adjustments are the latest action taken by an airline to deal with the rapid spread of the omicron variant.

Kirby said in a note posted to the company’s website on Monday that United are “cutting back our short-term schedules to ensure we have the staff and resources to take care of customers.” A spokeswoman on Tuesday declined to say how many flights the carrier is canceling.

United has around 3,000 workers who are currently positive for Covid, Kirby said in the staff note. This represents about 4% of its US workforce.

“Just as an example, in one day in Newark [New Jersey], almost a third of our workforce called the sick, ”Kirby said. He said none of the carrier’s vaccinated employees, who make up more than 96% of its staff, are hospitalized and that they have not had a Covid-related accident. deaths among employees vaccinated within eight weeks.

On December 31, United offered triple pay for pilots to travel for most of January. The pilots’ union said sickness calls among airmen were at an all time high. Southwest Airlines also gave pilots incentive pay for this month.