US airlines canceled about 800 more flights on Monday after nixing thousands of flights during the Christmas holiday weekend, as Omicron cases across the country rise, forcing crews to isolate and travelers to seek other forms of travel.

Shares of American Airlines Group Inc, United Airlines Holdings Inc, Delta Air Line Inc and Southwest Airlines Co were down between 2 per cent and 3pc in trading before the opening bell.

Nearly 740 flights were canceled within, into, or out of the United States by early Monday morning, a tally on flight-tracking website FlightAware.com showed.

The flight cancellations on Monday were on top of over 3,000 cancellations during the Christmas holiday weekend, typically a peak time for travel for Americans.

With rising infections, airlines have been forced to cancel flights, with pilots and cabin crew needing to quarantine, while poor weather in some areas added to travelers woes.