Investigators in France were to take charge of the crashed Ethiopian Airlines jet's black boxes on Thursday, seeking clues into a disaster that has grounded Boeing's global 737 MAX fleet and left scores of families mourning and angry.

Sunday's crash after take-off from Addis Ababa killed 157 people from 35 nations in the second such calamity involving Boeing's flagship new model in six months.

Possible links between the accidents have rocked the aviation industry, scared passengers worldwide, and left the world's biggest planemaker scrambling to prove the safety of a money-spinning model intended to be the standard for decades.

Relatives of the dead stormed out of a meeting with Ethiopian Airlines on Thursday, decrying a lack of transparency, while others made the painful trip to the crash scene.

"I can't find you! Where are you?" said one Ethiopian woman, draped in traditional white mourning shawl, as she held a framed portrait of her brother in the charred and debris-strewn field.

Nations around the world, including an initially reluctant United States, have suspended the 371 MAX models in operation, though airlines are largely coping by switching planes.

Another nearly 5,000 MAXs are on order, meaning the financial implications are huge for the industry.