More than 1,500 flights across the globe were scrapped on Sunday, bringing more misery for travellers planning to fly over the festive period.
As many as 5,900 flights have now been cancelled on Christmas Eve, Christmas Day and the day after, according to FlightAware data tracking website.
Chinese and US airlines appear to be the hardest hit. Further disruption is expected on Monday.
Companies have blamed staff shortages on the fast-spreading Omicron variant.
