BEIJING - China remains almost completely isolated from the rest of the world as it adheres to a strict Covid Zero policy, with flights in and out of Asia's biggest economy even lower than when the first cases of the virus were discovered in Wuhan in early 2020.

As air travel elsewhere springs back, data from flight information provider VariFlight shows little improvement in China-international flight options, with around 100 flights per day compared to more than 2,600 before 2020.

Scheduled flights dropped off even further after Shanghai imposed a weeks-long lockdown in April; they've never really recovered.

The situation for people wanting to get in and out has gotten so bad that the nation's expatriate business community is turning to private plane charters.

The American Chamber of Commerce in Shanghai is offering members stuck outside of China a charter flight from Los Angeles to Hangzhou later this month.

With China rushing to contain fresh virus outbreaks ahead of a pivotal Communist Party congress slated for October, more than 30 cities across the vast nation are either fully or partially locked down, according to Caixin.

The southwestern megacity of Chengdu - population 21 million - is still shut after a lockdown that started last week was extended through Wednesday.

On Tuesday, authorities sealed off parts of Guiyang, home to around 6.1 million.

China's Covid-19 border rules are so intensive, the US is protesting - by suspending flights.

The US Department of Transportation is halting 26 flights by Chinese airlines this month, saying Beijing's policies, which kick in if travellers test positive for Covid-19, are unreasonable.

The flight ban impacts several Chinese airlines including Air China, China Eastern Airlines and China Southern Airlines and is in response to China's suspension of 26 flights by US carriers since February - also shelved after virus cases were found onboard.

The US carriers impacted by Beijing limiting flights include United Airlines and Delta Air Lines. According to Civil Aviation Authority of China rules, if at least 4 per cent of passengers on a flight test positive for Covid-19 after arrival, one flight by that airline will be suspended. If the number reaches 8 per cent, two flights will be suspended.

That's actually an easing of previous standards that could suspend an airline's flights for two weeks or limit passenger loads to 40 per cent.

Germany laid on eight charters between May and September while the French and Swiss embassies have teamed up with their respective business chambers to offer similar private shuttles.

The AmCham flight, on an Airbus SE A340-300, is expected to depart around Sept 20, with economy-class fares starting from US$5,500 (S$7,700) and stretching to as much as US$22,000 in first, according to an email sent to members last week.

AmCham China said in its email that the charter flight was being offered "given the current difficulties many members face in returning to China".

The chamber is hoping demand is sufficient to warrant the charter flight and members had until last Saturday to express their interest.

The French charters carried a total of 750 people to Tianjin.

"Maintaining flights from France to China is essential for the French business community in China," the French Chamber of Commerce in China said in a LinkedIn post last month.

The Swiss charters between Hangzhou and Zurich will operate in around one week.

In one small sign of improvement, two-way flights between Britain and China have now resumed after a 20-month hiatus.

But the easing has only made a difference for mainland Chinese carriers, with British airlines facing their own scheduling and staffing issues. Air crew generally don't like flying to China due to its tough screening policies for Covid-19. BLOOMBERG