Talks are underway between the U.S. and China on possible changes to apparent new aircraft-cleaning requirements that prompted a Delta Air Lines flight to turn back to Seattle and that could upend air travel into the Asian nation.

The discussions were confirmed Tuesday by a State Department official who spoke on condition of anonymity. China's new sanitation mandates — spurred by the spread of Covid-19 — significantly extend the time planes are on the ground and largely copy steps that U.S. airlines already take to clean between flights, representatives for the industry said. There also is a shortage of available workers to carry out the added steps, they said.

The new requirements are part of the changes that countries and industries are making to try to slow the spread of the highly contagious omicron coronavirus variant.

China is committed to a zero tolerance policy toward Covid, which uses border curbs and increasingly stringent restrictions to try and keep out all cases of the virus. Vigilance has increased with the detection of the new omicron variant and with the Beijing Winter Olympics set to start in early February. Hong Kong, which follows a similar 'Covid Zero' strategy, is mandating a three-day hotel quarantine for air-cargo crews to thwart transmission of omicron.

The U.S. is seeking changes to the new Chinese cleaning mandates, since rigorous disinfecting procedures are already performed between flights by carriers globally, the State Department official said. Airlines put in place extensive on-board cleaning protocols early in the pandemic.

Delta's service to China "remains very fluid" as it evaluates the change in procedures that caused it to turn around a Dec. 21 flight to Shanghai, returning the plane to where it took off in Seattle. The carrier is assessing its twice-weekly trips from Detroit and Seattle to Shanghai on a flight-by-flight basis, a spokesman said Tuesday.

It wasn't immediately clear what sanitation procedures authorities in China recently put in place. A spokesman for Shanghai's airport declined to comment, while a spokeswoman for the Civil Aviation Administration of China, or CAAC, referred to a Covid control protocol issued in September.

In a government health briefing in Beijing on Wednesday, CAAC official Han Guangzu told reporters that China had laid out in September detailed plane-cleaning protocols aimed at preventing Covid's spread through aircraft.

Preventative disinfection needs to be undertaken at least once a month and on every day on planes that stop in medium or high-risk cities, Han said, citing the protocols. Cargo planes need to be disinfected if they contain goods that could spread disease, and a "thorough disinfection" of an aircraft needs to be done if it lands in China with an infected passenger on board.

Other airlines are also responding to the apparent shift.

United Airlines said it is working to comply with the mandate put in place last week and hasn't canceled any of its four weekly flights between San Francisco and Shanghai. American Airlines Group Inc.'s twice-weekly flight between Dallas-Fort Worth and Shanghai also is affected, the carrier said, without providing further details.

Airlines for America, the lobbying group for major U.S. carriers, declined to comment. The new rules apply to any airline flying into China.

In Asia, ANA Holdings Inc. has delayed departure times for flights out of Shanghai and Guangzhou since Dec. 22 to allow for the time it takes to clean planes, a spokesman for the Japanese carrier said. Japan Airlines Co.'s passenger flights to and from China are operating normally, although inbound air cargo into the country has been restricted, according to a spokesman.

U.S. carriers flying from the States stop first in another city, like Incheon in South Korea, and change crews before going on to China. The procedure ensures that flight crews don't surpass the legal number of hours they can work and allows them to avoid an overnight stay that could trigger additional Covid protocol requirements for the aircraft or crew, airline representatives said.

Delta's Flight 287 returned to Seattle after the carrier learned of the change in cleaning requirements midflight, the Atlanta-based carrier has said. In addition to the time required, the new procedures "are not operationally viable," Delta said.