A Chinese consulate in the United States has lodged a protest with an American airline after one of its China-bound flights returned to the US midway through the journey. “Several China-bound flights have been delayed or canceled recently, with one plane returning to the US after flying half of the journey,” the Chinese consulate in San Francisco said in its Twitter-like WeChat account on Sunday. “The consulate has lodged protests to the related airline.” It also reminded travellers to China to monitor schedules for changes and ensure they had completed tests for boarding. “The consulate will continue to urge US airlines to guarantee passengers’ legitimate rights and [travellers] not to travel to China unless necessary,” it said. “Please choose airlines with caution to ensure smooth travel.” China tightens controls as Omicron tests zero-Covid strategy The consulate did not name the airline but a 23-year-old Chinese film studies student, who would only identify herself as Runtu, said she was aboard Delta Air Lines flight DL287 to Shanghai on Wednesday when it returned to Seattle six hours into the journey. The pilot said the aircraft had to return because “China’s entry policy has temporarily changed, and the health code of all persons on the flight cannot be authenticated”, she said. Runtu said the flight from Seattle had already been delayed for a day. She said she was told that it was cancelled on Tuesday because there was a delay in take-off and the crew could not work overtime. A Delta Air Lines spokeswoman said on Sunday that flight 287 from Seattle to Shanghai returned to Seattle after “new procedures required at Shanghai Pudong International Airport were implemented while it was en route” to Shanghai. “The new procedures require longer time on the ground than Delta is able to schedule there,” the spokeswoman said, adding the carrier was working to rebook customers on alternative flights. Chinese embassy highlights aircrew shortage after Delta flight’s U-turn China has adopted a zero-tolerance policy on Covid-19 , and has rolled out even more stringent Covid-19 quarantine and border control rules to counter the threat of the Omicron variant, according to new measures announced on Monday. An employee at Shanghai Pudong International Airport said the requirements for international flights remained unchanged in the past few days, and the cancellation of the Delta flight was not related to the airport. “Other flights arrived normally that day, even some from the US,” the staff member said. Runtu said she was staying at a hotel arranged by the airline and was told that she might not be able to board another flight home until January 9. She said there were a number of other Chinese students on the flight and they were concerned that re-entering the US could affect their visas. They were also concerned about the need for further coronavirus tests to board rescheduled flights and whether their health codes to enter China would remain valid. “I am just taking it one day at a time,” Runtu said.