Around 11,500 flights have been cancelled worldwide since Friday as Omicron variant forced several countries to impose travel restrictions amid concerns over virus spread.
According to Flight tracker FlightAware, about 3,000 flights have been cancelled on Monday and 1,725 cancelled on Tuesday.
A total of 471 flights have been cancelled either into or out of the United States, the website data shows.
US airlines said the cancellations have been due to crew members testing positive for the coronavirus, reported BBC.
According to flight tracker data, the majority of the flights cancelled on Monday are those by Chinese companies. This includes 420 flights cancelled by China Eastern, and over 190 cancellations by Air China.
The hardest-hit US airlines on the other hand are United and JetBlue.
United said it cancelled 115 flights Monday, out of more than 4,000 scheduled, due to crews with Covid, reported the Associated Press.
The latest cancellations come at a time when more than 90 countries, largely the West, are reporting record Covid cases spurred by the Omicron variant.
Cases in the United States are already on track to reach record highs in January, fuelled by large pockets of unvaccinated residents as well as lack of access to quick and easy testing.
President Joe Biden on Monday said that some US hospitals could be “overrun” but that the country is generally well prepared to meet the latest surge and Americans need not “panic.”
In Europe, France and UK have been reporting more than 1,00,000 cases, with hospitalisations almost doubling over the past month.
In Belgium, the government imposed new measures starting Sunday that ordered cultural venues like movie theatres and concert halls to close.
In Netherlands, the Dutch government imposed a partial lockdown and shut down all non-essential establishments, restaurants and schools.
(With inputs from agencies)