A Boeing jet earmarked for China was returning to the United States on Friday, flight tracking data showed, as the planemaker's flagship delivery plant outside Shanghai was drawn into a deepening tariff war between Beijing and Washington.

Boeing faced new questions over the impact of tariffs on imports into China on Thursday as the spotlight fell on the fate of jets waiting at an aircraft completion plant near Shanghai. The U.S. planemaker was reported earlier this week to face a Chinese ban on its imports,