Travelers trek through Terminal E at Logan Airport, Tuesday, Dec. 21, 2021, in Boston. At least three major airlines say they have canceled dozens of flights, Friday, Dec. 24, because illnesses largely tied to the omicron variant of COVID-19 have taken a toll on flight crew numbers during the busy holiday travel season. Credit: AP Photo/Charles Krupa

Airlines continued to cancel hundreds of flights Saturday as staffing issues tied to COVID-19disrupted holiday celebrations during one of the busiest travel times of the year.

FlightAware, a flight-tracking website, noted 875 flights entering, leaving or inside the U.S. canceled Saturday, up from 689 Friday. About 200 more flights were already canceled for Sunday. FlightAware does not say why flights are canceled.

Delta, United and JetBlue on Friday had all said the omicron variant was causing staffing problems leading to cancellations. United spokesperson Maddie King said staffing shortages were still causing cancellations and it was unclear when normal operations would return. "This was unexpected," she said of omicron's impact on staffing. Delta and JetBlue did not immediately respond to questions Saturday.

According to FlightAware, the three airlines canceled more than 10% of their Saturday scheduled flights. European and Australian have also canceled holiday-season flights due to staffing problems tied to COVID.

Flight delays and cancellations tied to staffing shortages have been a regular problem for the U.S. airline industry this year. Airlines encouraged workers to quit in 2020, when collapsed, and were caught short-staffed this year as travel recovered.

  • Travelers wait in line to be tested for COVID-19 at Logan Airport, Tuesday, Dec. 21, 2021, in Boston. At least three major airlines say they have canceled dozens of flights, Friday, Dec. 24, because illnesses largely tied to the omicron variant of COVID-19 have taken a toll on flight crew numbers during the busy holiday travel season. Credit: AP Photo/Charles Krupa

  • A traveler pulls a ski bag on the way to the check-in counter for United Airlines in a terminal of Denver International Airport Friday, Dec. 24, 2021, in Denver. Major airlines canceled hundreds of flights Friday amid staffing shortages largely tied to the omicron variant of the coronavirus. Credit: AP Photo/David Zalubowski

  • Holiday travelers line up at the security checkpoint check point at Pittsburgh International Airport in Imperial, Pa., Thursday, Dec. 23, 2021. At least three major airlines say they have canceled dozens of flights, Friday, Dec. 24, because illnesses largely tied to the omicron variant of COVID-19 have taken a toll on flight crew numbers during the busy holiday travel season. Credit: AP Photo/Gene J. Puskar

To ease staffing shortages, countries including Spain and the U.K. have reduced the length of COVID-19 quarantines by letting people return to work sooner after testing positive or being exposed to the virus.

Delta CEO Ed Bastian was among those who have called on the Biden administration to take similar steps or risk further disruptions in air travel. On Thursday, the U.S. shortened COVID-19 isolation rules for only.

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