(Reuters) - More than 300 Boeing 737 MAX 8 and MAX 9 passenger jets around the world have been taken out of service following two fatal crashes over the past five months in Ethiopia and Indonesia that killed almost 350 people in all.

Ethiopian Federal policemen stand at the scene of the Ethiopian Airlines Flight ET 302 plane crash, near the town of Bishoftu, southeast of Addis Ababa, Ethiopia March 11, 2019. REUTERS/Tiksa Negeri

The causes of both crashes are under investigation. One of the biggest unanswered questions: Was the plane’s software to blame?

WHAT WE KNOW

- Boeing has stopped delivery of all new MAX jets to its customers after the crash in Ethiopia on March 10 that killed 157 people.

- Satellite data gathered from the Ethiopian Airlines flight and evidence from the crash site showed similarities with a Lion Air accident in Indonesia, prompting the U.S. Federal Aviation Administration (FAA) to ground all MAX jets.

- Investigators have found strong similarities in the ‘angle of attack’ data recorded by the Ethiopian Airlines flight cockpit recorder and data from the Lion Air jet, a person familiar with the matter said.

- Graphs of the two sets of data are “very, very similar,” the person said on Monday. The angle is a key flight parameter that must remain narrow enough to preserve lift and avoid an aerodynamic stall.

- A flight deck computer’s response to readings from an apparently faulty angle-of-attack sensor is at the center of an ongoing probe into the Lion Air disaster.

- Investigators who verified data extracted from the black box recorders of the Ethiopian Airlines plane have found “clear similarities” with the doomed Lion Air flight, the French BEA air accident authority also said on Monday.

- Investigators have found a piece of a stabilizer in the wreckage of the Ethiopian jet with the trim set in an unusual position similar to that of the Lion Air plane, two sources familiar with the matter said.

- The pilot of the Ethiopian Airlines flight had reported internal control problems and received permission to return. The pilot of the Lion Air flight, which crashed on Oct. 29 with the loss of all 189 people on board, had also asked to return not long after taking off from Jakarta.

- The Ethiopian Airlines flight had an unusually high speed after take-off before the plane reported problems and asked permission to climb quickly, said a source who has listened to the air traffic control recording.

- A voice from the cockpit requested to climb to 14,000 feet above sea level - about 6,400 feet above the airport - before urgently asking to return, the source told Reuters on condition of anonymity. The plane vanished from radar at 10,800 feet.

- Indonesia plans to speed up by about a month the release of an investigation report on the Lion Air crash, its transport safety committee said. It now plans to release the report between July and August, ahead of its previous schedule of between August and September.

- Following the Lion Air crash, Boeing said it was preparing a software upgrade for the jets. After the Ethiopia crash, the company said it would deploy that upgrade across the fleet in the coming weeks.

- Boeing maintains its new, fuel-efficient jets are safe, but supported the FAA decision to ground them. Fearing a financial hit and brand damage, investors have wiped around $29 billion off the company’s market value.

WHAT’S NEXT?

- U.S. lawmakers said the planes could be grounded for weeks to upgrade and install the software in every plane.

- Boeing plans to release upgraded software for its 737 MAX in a week to 10 days, sources familiar with the matter said on March 16.

- No lawsuits have been filed since the crash of Ethiopian Airlines Flight 302, but some plaintiffs’ lawyers said they expect that Boeing will be sued in the United States.

- Investigators are expected to release a preliminary report based on information they glean from the data and cockpit recordings captured by the two black boxes.

- A decision will be made by countries about whether and when to lift the grounding of the Boeing jets based on that information.

- Ethiopian Airlines said on March 16 that DNA testing of the remains of the passengers may take up to six months.