WASHINGTON (NYTIMES) - A year ago, the United States celebrated Independence Day largely by staying home. The country staggered into that Fourth of July holiday weekend, having set records for new coronavirus cases in six of the nine previous days.

About 600 people were dying with the virus each day. On July 2 last year, the country set what was then a record: 53,000 new reported cases. Governors were forced to slow their reopening plans - and in the months that followed, the pandemic grew much, much worse.

This year, reports of new cases are holding steady at 12,000 a day, the lowest since testing became widely available. The US average of fewer than 300 daily deaths from Covid-19 is a decline of 23 per cent over the past two weeks. Hospitalisations are also dropping.

Riding a wave of optimism, Americans are eagerly returning to their Fourth of July rituals, flocking to the roads and skies in the stiffest test yet for the nation's travel infrastructure since the pandemic shut the nation down in March last year.

About 48 million Americans are expected to travel over last Thursday (July 1) to Monday, a 40 per cent jump from last year, according to AAA, the automobile owners group. Of those, a record 43.6 million are predicted to travel by car, an 8 per cent increase from 2019.

Another 3½ million people are expected to fly, representing a 164 per cent increase from last year. United Airlines says that more than two million passengers have booked flights between last Thursday and Tuesday, five times the number that flew during the same weekend last year.

The airline announced this past week that it would place the largest order for airplanes in its history, underscoring the bullish outlook for domestic travel.

Ridership on Amtrak is at about 55 per cent of pre-pandemic levels, the highest level so far this year. For the Fourth of July weekend, it is at 80 per cent of what it was over the 2019 holiday, Amtrak spokesman Jason Abrams said.

"Travel is in full swing this summer, as Americans eagerly pursue travel opportunities they've deferred for the last year and a half," said Ms Paula Twidale, senior vice-president at AAA Travel. "We saw strong demand for travel around Memorial Day and the kick-off of summer, and all indications now point to a busy Independence Day."

Still, a precipitous drop in US coronavirus cases through the spring has levelled off. About 100 million people in the country have yet to receive a single vaccine shot, and the supply of vaccines far outstrips the demand.

The spread of the Delta variant remains worrisome for the unvaccinated, and there are 1,000 counties in the country where fewer than 30 per cent of residents are inoculated, said Ms Rochelle Walensky, director of the Centres for Disease Control and Prevention.

The White House plans to host 1,000 essential workers and military families on the South Lawn on Sunday, the largest gathering of President Joe Biden's tenure. The celebratory display is meant to signal that Mr Biden has delivered on his promise that Americans would return to some semblance of normal life by the holiday.

"This weekend, millions of Americans will be able to get together - back together, not just with their families and close friends for small backyard cookouts, but with their community for larger festivals, parades and fireworks, celebrating our country's July Fourth Independence Day and the progress we have made against the virus together," White House coronavirus coordinator Jeff Zients said on Thursday.

While the country has fallen short of Mr Biden's goal of getting shots to at least 70 per cent of adults by Sunday, the White House has put a positive spin on the numbers. Mr Zients noted last week that 70 per cent of Americans age 30 and older have received at least one shot.

Public health officials have been struggling to motivate the vaccine holdouts. A few airlines and airports are taking up the charge, trying to entice people to get the shots with sweepstakes. The Transportation Safety Administration still requires masks in airports, on airplanes and on trains.

While Americans are travelling again, many local officials are taking a cautious approach. Although New York City plans to revive its huge Macy's fireworks show, some large celebrations, parades and fireworks extravaganzas have been pared back or cancelled.

A few places, including Glencoe, Illinois, have postponed their fireworks shows until Labour Day, although neighbours and community groups will be allowed to parade through the village's downtown once again.