Boeing's newest version of its most popular plane is again in the spotlight after another deadly crash minutes after take-off.

The Boeing 737 MAX 8 operated by Ethiopian Airlines crashed after leaving Addis Ababa on Sunday en route to Nairobi, the capital of neighbouring Kenya, killing all 157 people on board.

Here's what we know:

It's the same model as in the Lion Air crash

The Boeing 737 MAX first entered service with airlines in 2017. ( Reuters: Pascal Rossignol )

The accident is strikingly similar to last October's Lion Air crash off Indonesia.

Both planes were new Boeing 737 MAX 8 models, the newest version of the single-aisle, narrow-body aircraft, and both crashed just minutes after take-off.

The Lion Air plane plunged into the Java Sea, killing 189 people.

The preliminary report in the Lion Air crash found the pilots struggled to control the plane as an automatic safety system designed to prevent stalling repeatedly pushed the plane's nose down.

Pilots had to manually raise the nose to correct the flight, only for the sequence to repeat about five seconds later.

This happened 26 times, but the pilot failed to realise what was happening.

Investigators believed faulty information from sensors could have activated the system.

The Lion Air plane nose-dived into the sea, leaving just tiny pieces behind. ( AP: Tatan Syuflana )

In the wake of the crash, US pilots who were trained to fly the same model said Boeing had not told them about the new anti-stall system in training documents.

Pilots said Boeing issued a safety bulletin after the crash that included new details on how to disable the system.

Was the anti-stall system at fault here?

We don't know.

The jet showed an unstable vertical speed after take-off, air traffic monitor Flightradar24 said, and the senior Ethiopian pilot sent out a distress call.

The plane was given clearance to return to the airport but crashed six minutes after departing, ploughing into the ground at Hejere near Bishoftu/Debre Zeit, about 50 kilometres south of Addis Ababa, at 8:44am (local time).

The weather was clear at the time of the crash.

Map The doomed Ethiopian Airlines flight

Safety experts are cautioning against drawing too many comparisons between the Ethiopian Airlines and Lion Air crashes until more is known about Sunday's disaster.

But William Waldock, an aviation safety professor at Embry-Riddle Aeronautical University, said suspicion would be raised because the same type of plane appeared to crash the same way — a fatal nosedive that left wreckage in tiny pieces.

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"Investigators are not big believers in coincidence," he said.

Mr Waldock said Boeing would look more closely at the flight management system and automation on the MAX.

But he noted it was very early, and more would be known after investigators found and analysed the Ethiopian plane's black boxes.

Former US National Transport Safety Board (NTSB) chairman Mark Rosenker said the catastrophic crashes of two new airplanes soon after the 737 MAX 8 was introduced were "highly unusual" and both had broad similarities.

He said it was "now an extraordinary issue" for aviation safety officials to grapple with and would prompt a sweeping investigation.

Alan Diehl, a former NTSB investigator, said the similarities included both crews encountering a problem shortly after take-off, and reports of large variations in vertical speed during ascent, "clearly suggesting a potential controllability problem" with the Ethiopian jetliner.

But there are many possible explanations, Mr Diehl said, including engine problems, pilot error, weight load, sabotage or bird strikes.

He said Ethiopian Airlines had a good reputation, but investigators would look into the plane's maintenance, especially since that may have been an issue in the Lion Air investigation.

The Ethiopian plane was new and had been delivered to the airline in November.

Its last maintenance was on February 4, and it had flown just 1,200 hours.

Boeing said in a statement it was ready to assist in any investigation into the crash in Ethiopia.

Do Australian airlines use the 737 MAX?

Not yet, but Virgin Australia has ordered 30 of them.

The first of those are due to start flying at the end of the year, a Virgin Australia spokesman said.

Ethiopian Airlines had also ordered 30 of the planes and five were in operation before the fatal crash.

Around the world, just under 350 737 MAXs have been delivered by Boeing, as of January.

The MAX 8 is the newest version of a jet that has been a fixture of passenger travel for decades and the cash cow of the world's largest aircraft maker, competing against Airbus SE's A320neo family of single-aisle jetliners.

The decades-old 737 family is considered one of the industry's most reliable aircraft.

Boeing rolled out the fuel-efficient MAX 8 in 2017 as an update to the already redesigned 50-year-old 737.

Will airlines suspend the 737 MAX?

Ethiopian Airlines has grounded all its Boeing 737 Max 8 aircraft as a safety precaution following the crash.

Ethiopian Airlines was using five new 737 Max 8 planes and was awaiting delivery of 25 more.

China has asked domestic airlines to ground all their 737 MAX jets, according to Bloomberg.

The Asian powerhouse is one of the biggest customers of the new 737 MAX model, with dozens of them in operation for Chinese airlines.

Cayman Airways separately announced it would suspend operations by its two 737 MAX planes "until more information is received".

Boeing says its plane is safe. The company's sales didn't suffer after the Indonesia crash, and its stock price has soared.

How is the crash affecting Boeing's other aircraft?

In the wake of the crash, Boeing announced it had postponed the planned ceremonial debut of its 777X widebody aircraft in Seattle.

A Boeing spokesman said there was no delay to the 777X program, but said the company was focused on "supporting" Ethiopian Airlines in the wake of the crash.

"We will look for an opportunity to mark the new plane with the world in the near future," the company said.

AP/ABC