Thousands of flights cancelled as US digs out from deadly superstorm

Thousands more flights have been cancelled across the United States, with no end in sight to days of travel misery as the country digs out from a deadly superstorm.

Southwest Airlines was still days away from resolving its systemwide breakdown: the carrier cancelled more than 2,500 flights on Wednesday, accounting for nearly 90 percent of all scrubbed US flights, according to tracking website FlightAware.

Officials in Erie county in western New York — the area of the country hardest hit by the massive winter storm — lifted their death toll to 34, taking the national total to at least 56.

Around-the-clock work to restore electricity continued in the county's main city of Buffalo, with the number of outages down to 500 residents, Mayor Byron Brown tweeted early on Wednesday.

Another kind of crisis was playing out at US airports around the country, as Southwest Airlines was forced to cancel thousands more flights to try to recover from a spiralling logistics breakdown.

The airline's woes stranded thousands of customers as well as pilots and flight attendants.

The storm, which descended on the United States just before the busy Christmas holiday weekend, led to unusually cold weather in much of the country, including southern states like Texas and Florida.

READ MORE: 'Blizzard of the century' pushes US death toll to 50

Southwest 'optimistic'

In a series of media appearances, Transportation Secretary Pete Buttigieg recounted telling Southwest Chief Executive Bob Jordan that the government would "hold them accountable" in requiring the airline to compensate customers for the mounting costs of cancelled flights and travel-related expenditures.

Jordan said he was "truly sorry" and promised to "make things right for customers," according to a video statement posted to Southwest's website.

"We're optimistic to be back on track before next week," he added.

Jordan has acknowledged that the problems have underscored the need to upgrade outdated trip scheduling software that became overwhelmed in the storm.

The problem has been highlighted by the flight attendants union, which has called on Southwest to invest more in employees. Several leading Southwest unions remain locked in contract negotiations after earlier pacts expired.

Another union, the TWU Local 555, which represents ground workers, said the meltdown reflected Southwest's failure to adapt its systems as its operations have evolved.

"Although it can be complicated, especially during the holiday season, we need to consider better spacing of flights during extreme weather events in the bitter cold of winter — as well as the extreme heat of summer," said Local 555 President Randy Barnes.

In times of extreme weather, "we should consider slowing the entire schedule," Barnes said.

READ MORE: Dozens dead in major US winter storm

Ninety percent of deaths in Buffalo

Temperatures were moderating nationwide on Wednesday, including in Buffalo, even as the region remained in triage mode.

The city, on the shores of Lake Erie near the Canadian border, has seen a majority of storm-related fatalities.

As temperatures plummeted Friday night, commuters and some residents fleeing their freezing homes became trapped on highways, with first responders unable to reach them.

Of the confirmed deaths, three bodies were yet to be identified, Erie County Executive Mark Poloncarz told a news conference.

The National Guard planned to conduct door-to-door wellness checks for every home in areas that lost power, Poloncarz said on Twitter, while reiterating that a driving ban was still in effect for Buffalo.

"We know that some people are low on food," he said. "We have rations available at area warming centers. Please work with neighbours and friends, walk to open stores if possible."

READ MORE: Power outages, travel snarls as deadly winter storm hits the US