As many as 11,500 flights have been cancelled across the world since Friday as Covid-induced restrictions hit global travel and the chaos that ensued over the Christmas weekend spilled over onto Monday and Tuesday.

       The cancellations and disruptions come amid a global surge in cases of the Omicron variant of the coronavirus.

       Flight tracker FlightAware said about 3,000 flights have been canceled on Monday while 1,725 have been cancelled for 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.

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       According to FlightAware, 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 canceled 115 flights Monday, out of more than 4,000 scheduled, due to crews with Covid, reported the Associated Press.

       The Centres for Disease Prevention and Control (CDC) announced on Monday that it recommends that the isolation period for asymptomatic Covid cases be halved from ten to five days in a bid to blunt mass Omicron-induced disruption, reported AP.

       The guidelines add that the five-day isolation period should be “followed by five days of wearing a mask when around others.”

       The change has been guided by early research that suggests that the Omicron variant causes milder illness in comparison to earlier variants like Delta.

       The CDC predicted a surge in Omicron-driven cases but said that not all cases will be severe.

       “Not all of those cases are going to be severe. In fact many are going to be asymptomatic,” said CDC director Rochelle Walensky to AP.

       CDC data shows that as of Monday, 61.8 per cent of the US population has been fully vaccinated while 32.3 per cent have received booster doses of Covid-19 vaccines.

       The US has been the worst-hit nation where 816,000 people have lost their lives to the pandemic.

       With the global surge in cases of the Omicron variant, the US has recorded 250,000 cases since last January.

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       The recent surge has been fuelled by large numbers of unvaccinated residents as well as lack of access to quick and easy testing.

       Dr Anthony Fauci, the country’s top infectious disease expert, said that the US should also consider imposing a vaccination mandate for domestic travel as another way to push people to get vaccinated.