According to Flightaware's website, at 20:40 on 25 December there were more than 2,650 flight cancellations, of which 940 were travel related to the United States, whether international or domestic.
More than 6,350 flights were also delayed worldwide.
As of Friday, around 2,400 cancellations and nearly 11,000 delays were identified, according to the same source, who already has more than 900 cancellations scheduled for today (26 December).
Pilots, flight attendants and other crew members had to be quarantined after being exposed to covid-19, which forced Lufthansa, Delta and United Airlines to cancel flights.
"The spike in Omicron cases across the country this week has had a direct impact on our crews and the people who run our operations," said the US airline, assuring it is working to find solutions for affected passengers.