BEIJING (AP) — Delta Air Lines says new pandemic-related cleaning requirements at a Shanghai airport were behind the turning back of a recent flight from Seattle in midair. The move prompted a protest from the Chinese Consulate in San Francisco. An emailed statement from Delta says the new mandates at Shanghai Pudong International Airport require significantly extended ground time and are not operationally viable for Delta. It isn’t clear what the rules are and what prompted the change. It comes as China tightens its already strict COVID-19 travel restrictions in the face of a growing outbreak in the city of Xi’an and ahead of the Winter Olympics in Beijing in six weeks. The city of 13 million people has been locked down.