Trade power tensions, regulatory hurdles and attempts by the West to counter Chinese competition are delaying a return of the 737 Max in China, frustrating Boeing Co. as a potential rival demonstrates its growing influence.

Six months after the West lifted an almost two-year flight ban on the Max, there is no clear end in sight for the crisis surrounding Boeing's fastest-selling jet in China — the first nation to ground it in 2019 after two deadly crashes in five months.

The company had hoped for China to approve the Max to return to the sky by the end of last year; in January 2021, Boeing said it expected the Max to be approved by regulators everywhere by the end of June. Now, with help from the Biden administration, Boeing is stepping up efforts to convince China the plane is safe and reset its most strategic partnership as airlines start to recover from the COVID-19 pandemic.