New York, Jan 1 (IANS): The latest surge of coronavirus with the variants of Omicron and Delta combined has kept the US in complicated chaos of understaffed medical services as well as cancelled flights, while the federal government still pins hope on its vaccination policy to turn the table, sooner or later.

With more than 580,000 Covid-19 cases on Thursday, the US shattered its own record for new daily coronavirus cases, beating a milestone it already broke on Wednesday. Thursday's count toppled the 488,000 new cases on Wednesday, which was nearly double the highest numbers from last winter, Xinhua news agency reported.

"The back-to-back record-breaking days are a growing sign of the virus's fast spread and come as the world enters its third year of the pandemic," reported The New York Times (NYT), noting that hospitalisations and deaths, however, have not followed the same dramatic increase, further indication that the Omicron variant seems to be milder than Delta and causes fewer cases of severe illness.

In the past two weeks, deaths are down by five per cent with a daily average of 1,221 while hospitalisations increased by just 15 per cent to an average of 78,781 per day, it added.

Urgent care centres across the US are grappling with what to do as the fast-spreading Omicron variant hits employees and the demand for Covid-19 testing surges. "In some instances, they are closing certain locations for a few days," reported The Wall Street Journal on Friday.

More people are turning to the non-emergency clinics for Covid-19 testing, and at-home test kits are hard to come by. As at airlines, which have canceled thousands of flights this December, workers at urgent care centres are testing positive for coronavirus and are unable to work, said the report.

CityMD, a chain of urgent care clinics in the New York City area, closed 31 of its locations in recent weeks, including 12 on Wednesday. A spokeswoman said more locations could close. Northwell Health-GoHealth Urgent Care temporarily closed about 10 of its 55 locations in New York in recent days.

Heading into the New Year's weekend, when return flights will produce another crest in air travel, airlines have been canceling more than 1,000 flights a day to, from or within the US.

"Carriers and their employees say the latest chapter of the pandemic, the Omicron variant, has cut deeply into the ability to staff flights, even though a vast majority of crew members are vaccinated," reported NYT on Thursday.

JetBlue has been one of the airlines hardest hit, canceling 17 per cent of its flights on Thursday, according to the air travel data site FlightAware.

The carrier said on Wednesday that it would cut about 1,280 flights through mid-January, citing the rise in virus cases in the Northeast, where its operations and crews are concentrated.

As many as 10 million people may fly from Thursday through Monday, according to Transportation Security Administration estimates. For months, airlines have been preparing reserves of workers for the holiday crush, but "those measures were inadequate in a fast-changing situation, and many passengers were frustrated," said the report.

The rapid surge of Omicron infections in the US may be relatively brief, measured in weeks rather than months, according to infectious-disease experts who have been astonished by the speed of the coronavirus variant's spread and who are hoping this wave ebbs just as quickly, reported The Washington Post on Thursday.

Some forecasts suggest coronavirus infections could peak by mid-January.

"Omicron will likely be quick. It won't be easy, but it will be quick. Come the early spring, a lot of people will have experienced Covid-19," William Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health, was quoted as saying.

On Thursday, the Joe Biden administration told the Supreme Court that federal law gives it the authority to impose a nationwide vaccine or testing requirement for large employers, and the court should not stand in the way of a program that will save thousands of lives, the report added.

"The nation is facing an unprecedented pandemic that is sickening and killing thousands of workers around the country, and any further delay in the implementation of the (requirement) will result in unnecessary illness, hospitalisations and deaths because of workplace exposure" to the coronavirus, said a federal filing.

The Supreme Court has announced a special hearing on January 7 to consider challenges to the rules from the Occupational Safety and Health administration. It was upheld by a panel of the US Court of Appeals for the 6th Circuit earlier this December, but is being challenged by a coalition of business groups and Republican-led states.