By Jamie Freed

April 7 (Reuters) - A Boeing Co 737 MAX meant for China Eastern Airlines subsidiary Shanghai Airlines is due to fly from Guam to Shanghai on Thursday, flight tracking websites showed, amid uncertainty over when the model will resume flying in China.

The planned flight BOE631 comes more than three weeks after the first 737 MAX bound for a Chinese customer since a 2019 grounding began its journey from Seattle to Boeing's completion plant in Zhoushan.

The plane, Situs Judi Slot Online 24Jam painted in Shanghai Airlines livery, has been stuck on the ground in Guam since March 15 due to a minor technical issue.

Boeing did not respond immediately to a request for comment.

The planned flight to Shanghai, which is in the middle of a strict COVID-19 related lockdown, comes as Chinese authorities scrutinise China Eastern's safety processes following the crash of a 737-800 on March 21 that killed all 132 people on board.

While that model is the predecessor to the MAX, analysts have expressed concern it could set back Boeing's efforts to regain ground in the world's biggest aircraft market and deliver more than 140 737 MAX jets already constructed for Chinese customers.

China's aviation regulator in early December provided airlines with a list of fixes required before its return to commercial flying, which it predicted would occur by the beginning of this year.

So far, however, there have been only test flights.

China Eastern has grounded all 223 of its 737-800 planes as a precaution while the crash is investigated. Chinese authorities are leading the investigation but the U.S. National Transportation Safety Board is helping them to read the plane's black boxes.

Depending on the results of the probe, China Eastern risks consequences including fines, aircraft groundings and unfavourable treatment when applying for new routes and airport slots, Morningstar analyst Cheng Weng said. (Image: https://cdn.slidesharecdn.com/ss_thumbnails/epapersurya13agustus2013-130812114346-phpapp02-thumbnail-3.jpg) China Eastern has not released any forecast of when it expects MAX deliveries to resume, though rival China Southern Airlines said last week it could take some of the planes this year.

(Reporting by Jamie Freed in Sydney; additional reporting by Eric M. Johnson in Seattle Editing by Shri Navaratnam)