NEW YORK (AP) — 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 888 flights entering, leaving or inside the U.S. canceled Saturday, up from 690 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 flight 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. American Airlines also canceled 90 flights Saturday, about 3% of its schedule, according to FlightAware. American spokesperson Derek Walls said the cancellations stemmed from “COVID-related sick calls” and the airline contacted customers on Friday. European and Australian airlines have also canceled holiday-season flights due to staffing problems tied to COVID.