United Airlines is offering its pilots triple pay to pick up trips for most of January to help ease a staffing shortage driven by the rapid spread of the omicron variant of Covid-19.

United, Delta Air Lines, JetBlue Airways, SkyWest, Alaska Airlines and other carriers have cancelled more than 10,000 combined flights since Dec. 23, citing a combination of bad weather and a surge in sick calls from crews that tested positive for Covid.

The disruptions come during what airline executives forecast as the busiest days since the start of the pandemic.

On Friday, airlines canceled nearly 1,500 U.S. flights, according to flight-tracking site FlightAware. United canceled more than 200, about 11% o f its mainline schedule.

United and the pilots ‘union, the Air Line Pilots Association, reached an agreement for higher pay to cover open trips, Bryan Quigley, United’s senior vice president of flight operations said Friday in a staff note, which was seen by CNBC.

Pilots will be offered three-and-a-half times their pay for flying open trips between Dec. 30 and Jan. 3 and triple pay for picking up trips between Jan. 4 and Jan. 29, the note said.

“Due to the rapid spread of the COVID Omicron variant, we are currently seeing record levels of pilot sick calls,” the pilots’ union wrote to its members. “The impact on the operation is clear and United has experienced a correspondingly large number of cancellations over the past week.”

United’s flight attendants are also getting extra pay to pick up trips and other airlines including JetBlue, American, Southwest and Spirit have also jacked up crew pay to avoid holiday flight disruptions.