Tens of thousands of airline passengers have been hit by the grounding of thousands of flights as a surge in Covid cases causes staff shortages.
More than 7,500 flights have now been cancelled since Friday, This will be the case over the Christmas weekend, according to the FlightAware data tracking website.
Chinese and US airlines are the hardest hit, with further delays and cancellations on Monday.
Companies say the cancellations are due to airline crews testing positive.
Staff who have not tested positive but had contacted with those infected are then being forced to self-isolate.
Recorded Covid cases are rising sharply around the world, largely driven by the Omicron variant.
New Restrictions Declared
European government have taken new measures as a surge of COVID-19 cases swept across the continent.
In some parts, the increase has been compounded by the emergence of the new Omicron variant, first detected in South Africa.
Italy, Spain and Greece have made face masks compulsory outdoors again during Christmas.
Catalonia, in northern Spain, has imposed an overnight curfew, and the Netherlands is in a strict lockdown.
Despite early findings that Omicron is milder than other variants, scientists are concerned by the number of cases.
The UK, France and Italy reported last week record infections
In the US, daily Omicron cases have risen beyond the peak of the recent Delta wave. Hospitals are filling up across the country.
Scientists believe Omicron could spread more easily than Delta. It could out-compete Delta to become the dominant variant in the UK.
But much is still unknown. It could still take weeks to understand how severe illness from the variant is and what it means for the effectiveness of vaccines.
The World Health Organisation (WHO) has earlier warned in a new press statements about the Covid-19 surge in the European continent.
