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(AP, WJW) — Airlines canceled hundreds more flights Sunday, citing staffing problems tied to COVID-19, as the nation’s travel woes extended beyond Christmas, with no clear indication when normal schedules would resume.

More than 700 flights entering, leaving or flying within the U.S. were called off, according to the flight-tracking website FlightAware. That figure was down from nearly 1,000 on Saturday. More than 50 flights were already canceled for Monday.

Cleveland Hopkins Airport says it’s best to know before you go by checking your flight status ahead of time. You can do that here.

Akron Canton Airport flights can be checked here.

Delta, United and JetBlue have blamed the omicron variant of the coronavirus for staffing shortages that forced cancellations.

“This was unexpected,” United spokesperson Maddie King said of omicron’s impact on staffing.

Globally, airlines scrapped about 2,200 flights as of Sunday morning, down from more than 2,800 from the day before, FlightAware’s data showed. The site does not say why flights are canceled.

JetBlue scrapped 10% of its flights Sunday. Delta canceled 5% and United canceled 4%, according to FlightAware. The three airlines canceled more than 10% of their scheduled flights on Saturday.

American Airlines spokesperson Derek Walls said the Christmas cancellations stemmed from virus-related sick calls.

Also Sunday, the nation’s top infectious disease doctor acknowledged that he was frustrated with the limited supply of COVID-19 tests.

Demand for tests has risen amid the surge fueled by the omicron variant. “We’ve obviously got to do better,” Dr. Anthony Fauci said an interview that aired Sunday on ABC’s “This Week.”

“I think things will improve greatly as we get into January, but that doesn’t help us today and tomorrow,” Fauci said.

Fauci said he was pleased with evidence that omicron causes less severe illness for most people. But he warned against complacency because the rapid spread of the disease could “override a real diminution in severity,” because so many more people could get infected.