Boeing is upgrading the stall prevention software on its 737 MAX, industry sources said Friday, as French investigators scoured black box data from the latest of two deadly crashes involving the aircraft in recent months.

The MAX has been grounded worldwide following Sunday’s Ethiopia Airlines disaster that killed all 157 on board, and the fallout has left the company, regulators and airlines scrambling to respond.

Boeing will fine-tune its MCAS system — implicated in the crash of a Lion Air 737 MAX 8 in Indonesia in October — within 10 days, said two sources, who cautioned that the cause of the latest crash has yet to be determined.

Boeing has halted deliveries of its top-selling model ahead of the software patch, which was already underway prior to the latest incident near Addis Ababa.

Asked for details about the timeline for the fix, a Boeing spokesman Friday would only say it would be installed in “coming weeks.”

The black boxes from the Ethiopian craft, which was only a few months’ old and crashed minutes after take-off, are being analysed by the French authorities to determine the cause of the accident.

An Ethiopian delegation delivered the cockpit voice and flight data recorders, which were damaged in the disaster, to France’s BEA air safety agency to begin the investigation on Friday.

The Lion Air crash also came just minutes after takeoff, killing 189 people, and US authorities say there is evidence of similarities between the accidents.

The Federal Aviation Administration (FAA) said findings from the crash site and “newly refined satellite data” warranted “further investigation of the possibility of a shared cause for the two incidents.”

Several American pilots also reported issues with the MCAS and the FAA said it had ordered Boeing to issue a fix by April.

The aerospace giant held a conference call on Thursday with at least three carriers using the 737 MAX and gave them the patch, one source said, and the other airlines will get it early next week.

Meanwhile, American pilots have raised questions about the training provided to the flight crews.

One who flew a MAX 8 on Monday told AFP that US-trained pilots — many of whom come from the military — would have been able to react quickly to the MCAS flaw, if that occurred in the accident last weekend.

And Captain Chesley “Sully” Sullenberger — noted for his safe landing of a damaged plane on the Hudson River in New York without loss of life — questioned the lack of experience of the Ethiopian first officer on the doomed flight, who reportedly had only 200 hours of flight time.

“A cockpit crew must be a team of experts, not a captain and an apprentice,” he said on social media.

But he also worried about the lag in getting a software fix installed.

“It has been obvious since the Lion Air crash that a redesign of the 737 MAX 8 has been urgently needed … and the announced proposed fixes do not go far enough.” (AFP)

• Employees work in the cargo hold of a Boeing 727 MAX 9 test plane outside the company’s factory, on March 14, 2019 in Renton, Washington.