NOTE: this article has been updated to reflect the cancellations as of 11:00 a.m. eastern time Monday.

(The Center Square) – Monday began with thousands of more flight cancellations globally and nearly 5,000 delays as airlines continued to struggle with staffing issues during this holiday travel season.

Domestically, 956 flights within, into or out of the U.S. were canceled as of noon eastern Monday, according to the tracking site FlightAware. An additional 2,421 flights in the U.S. were delayed.

Globally, more than 2,500 flights were canceled Monday as Christmas travelers sought to return home. More than 7,600 international flights were experiencing delays.

United Airlines canceled 93 flights as of noon Monday, American canceled 81 and Delta, 73.

The omicron variant, the dominant coronavirus variant currently infecting people in the U.S., is being blamed for much of the staffing shortages. Omicron is significantly more transmittable than earlier variants but early studies indicate its symptoms are far less severe on most individuals who contract it.

Bad weather in certain locations also is leading to cancellations.

JetBlue canceled 66 flights as of Monday morning, followed by Delta with 56 cancellations. Southwest has canceled 48 flights; Spirit, 36.

On Sunday, more than 1,500 flights within, into or out of the U.S. were canceled, while more than 3,200 were canceled globally.