Sunday's still unexplained crash of the passenger jet, just after take-off from Addis Ababa en route to Nairobi, killed 157 people and followed another disaster involving a 737 MAX in Indonesia five months ago that killed 189 people.

Ethiopian Airlines said on Wednesday it would send the black boxes from its crashed Boeing 737 MAX abroad, while a Norwegian airline sought compensation from the U.S. planemaker after two thirds of that model were grounded globally.

That has spooked the global airline industry and heaped pressure on Boeing, whose shares have plunged.

Multiple nations have suspended the 737 MAX, leading to the grounding of about two-thirds of the 371 jets of that make in operation around the world, according to Reuters calculations.

With no link proven between the two crashes, however, the United States has bucked the trend and allowed 737 MAX planes to continue operating even though Europe has suspended them.

Boeing, the world's biggest planemaker, has said it retains "full confidence" in the 737 MAX. Its shares fell 6.1 percent on Tuesday, bringing losses to 11.15 percent since the crash, the steepest two-day loss for the stock since July 2009.

The drop has lopped $26.65 billion off Boeing's market value.

Adding to the pressure on Boeing, Norwegian Air said it would seek recompense for lost revenue and extra costs after grounding its 737 MAX aircraft.

"We expect Boeing to take this bill," Norwegian said in an emailed statement to Reuters.

In Ethiopia, which lacks the forensic capabilities of other countries, a spokesman for Ethiopian Airlines said the black box voice and data recorders recovered on Monday would be sent overseas for analysis.

"There is no capacity here so the black box will be sent elsewhere for analysis. The investigation team will decide where," the spokesman told Reuters.

That could be in Europe, the company's CEO told CNN.

U.S. officials said the black box devices suffered some damage but they were confident of some initial results within 24 hours of the data being downloaded.

More than a dozen relatives of those who perished in the crash, mainly Kenyans who have flown in, left Addis Ababa early in the morning to pay their respects at the rural crash site where Flight ET 302 came down in a fireball.

It may take weeks or months to identify all the victims, who include a prize-winning author, a soccer official and a team of humanitarian workers.