Americans returning home from holiday travel had to battle another day of airport chaos Sunday, with more than 2,000 flights cancelled due to bad weather or airline staffing woes sparked by a surge in Covid cases.

Further disruptions are predicted for Monday, as a winter storm blows eastward.

As of 20H30 GMT Sunday, 2,432 domestic flights or international ones starting or finishing in the United States had been cancelled -- almost as many as the 2,749 scrapped over the course of Saturday, said the flight-tracking service FlightAware.

That midday figure represented well more than half of the 4,079 flights cancelled around the world. Another 5,004 US flights were delayed.

Southwest Airlines, one of the hardest-hit carriers, had to cancel some 400 flights Sunday morning, a spokesperson said in an email to AFP, adding that it expected further cancellations.

On Saturday, poor weather, much of it linked to Winter Storm Frida, forced Southwest to cancel 490 flights, most of them in the centre-north states south of the Great Lakes and reaching west to the Great Plains.

The result: intense frustration for many travellers.

Missed connections

"Our flight this morning was cancelled. We were now forced to rent 4x4 cars to drive all the way to Colorado from Texas," Southwest passenger Katie Armstrong posted on Twitter.

A woman named Kayla described her own ordeal: "I was supposed to get home at 10:30 yesterday morning. and at this point, I’ve had 3 flights cancelled and one delayed to the point where I missed my connection."

Airports in Chicago -- a major transit hub -- were the most affected Saturday, but by Sunday the airports in Atlanta, Denver, Detroit, Houston and Newark were also hard hit.

Around the world, air traffic has suffered snarls since Christmas because of airline staffing issues linked to the spread of the highly contagious Omicron coronavirus variant.

Many pilots and flight attendants have called in sick after testing positive for the virus or being forced to quarantine due to contact with someone who has the virus.

This has left carriers with staffing shortages and forced them to delay or cancel flights.

The latest travel chaos carried echoes of a frustrating Christmas weekend when around 7,500 flights around the world were scrapped.

And rebooking cancelled flights has been a major challenge for many.

One traveller, Eric Crawford, described his frustration at trying to call a Delta Airline agent to reschedule.

"An estimated wait time of 22+ hours to speak with a rep about a cancelled flight," he said on Twitter, "is not the best look for starting 2022."

And Kowshick Boddu offered this account, also on Twitter, about his troubles with Alaska Air: "We were supposed to fly out from Fairbanks to San Jose on Dec 30, but our flights got rescheduled to today which is eventually cancelled again??? Long customer call wait hours, no response and flights not been rebooked? Need help!!"

Travel woes are expected to continue into Monday, the first working day of 2022.

Storm Frida will continue on a disruptive path eastward, meteorologists said, bringing snow to a wide swath from Washington located on the mid-Atlantic coast up to Boston, Massachusetts in the north.

Nearly 575 Monday flights have already been cancelled within, into or out of the United States.