More than 2,400 U.S. airline flights were cancelled on New Year’s Day due to bad weather and an increase of omicron infection among staff. This has caused disruption in air travel across the entire year.

Flight-tracking website FlightAware reports that airlines have cancelled more than 12,000 U.S. flight cancellations since Christmas Eve. They have also been forced to defer thousands of more flights.

These travel problems occur during the peak days of the pandemic. The Transportation Security Administration had to screen nearly 580,000,000 people last year. This is a 79% increase over 2020, but still a 30% decrease from the 2019 pandemic.

Southwest AirlinesAlthough it had managed to avoid some of the disruptions which affected competitors over the holiday, FlightAware reports that 472 flights were cancelled on Saturday. This represents 13% of its scheduled flight schedule. Before a winter storm, the airline had suspended all operations from Chicago’s airports.

More than 200 flights depart daily from Chicago Midway International Airport. A spokeswoman for the airline stated that they had cut the flights because of “anticipating gusty winds, blowing snow, that decade-long history in Chicago Midway International Airport show us will slow the airspace down and make it very difficult to deicing or getting the aircraft back in the air.”

Many of the New Year’s Day cancellations were due to weather, but carriers included United Airlines, Delta Air LinesAnd JetBlue AirwaysMany flights were cancelled over the holiday period due to omicron infection among crew members.

Airline executives have increased incentives for flight attendants as well pilots in order to take more flights. This will help to ease the staffing shortfalls, which some executives believe could persist several more weeks.

United Pilots Union, The Air Line Pilots Association was negotiated triple payCNBC reports Friday that aviators can take up open flights through January. United crews SpiritOther people are receiving extra money to take up trip bookings.

This week, the Federal Aviation Administration also stated that disruptions will likely persist.

In a Friday statement, the agency stated that “weather and heavy-seasonal traffic will likely cause some travel delays in coming days.” A higher number of FAA workers have been found to be positive for COVID-19, just like the rest of America. To maintain safety, traffic volume at some facilities could be reduced, which might result in delays during busy periods.”

In order to avoid customers getting stuck at airports, airlines have attempted to cancel flights before they happen. JetBlue AirwaysThis week, it announced that 1,280 flights would be trimmed from its flight schedule until mid-January in order to prevent last-minute cancellations due to omicron Covid infection sidelining crews.

American AirlinesFlightAware data shows that, which runs a major hub from Chicago’s O’Hare International Airport on Saturday, cancelled 205 flights or 7%. Chicago-based United cancelled 53 flights or 7% its mainline flights.