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 7,000 flights have now been cancelled since Friday and over the Christmas weekend, according to the FlightAware data tracking website.
Chinese and US airlines appear to be the hardest hit, with further delays and cancellations announced for Monday.
Companies say the cancellations are due to airline crews testing positive.
Staff who have not tested positive but have been in contact 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.
Despite early findings that Omicron is milder than other coronavirus variants, scientists are concerned by the sheer number of infections being recorded.