BEIJING—China’s aviation regulator cleared the Boeing 737 Max on Thursday to return to flight, with technical upgrades, more than two years after the plane was grounded worldwide following two fatal crashes. China is the last major market where the Boeing 737 Max was awaiting approval after the United States allowed flights to resume in December 2020 and European Union regulators gave permission in January. Brazil and Canada have also given approval. Governments grounded the Boeing 737 Max after a total of 346 people were killed in the crashes of a Lion Air flight in Indonesia on Oct. 29, 2018 and an Ethiopian Airlines flight on March 10, 2019. Investigators blamed a computer system that pushed the plane’s nose downward during flight that couldn’t be overridden by pilots. Chinese pilots will need to complete new training before commercial flights can begin, the Civil Aviation Administration of China said on its website. …