Black box data recorders from Ethiopian Airlines flight 302 have arrived in France for analysis with the hope of determining what brought down the Boeing 737 Max jet on Sunday near Addis Ababa. The US on Wednesday joined a global ban on the 737 Max, ordering planes to remain on the tarmac.
"Evidence-based decisions are being taken, which in itself is a positive step," said Adrian Young, an expert in aviation safety with the To70 consultancy firm.
The US Federal Aviation Administration (FAA) said in a statement that the grounding was based on satellite tracking data and evidence collected from the crash site.
Ethiopian Airlines flight 302 to Nairobi crashed shortly after take-off, killing all 157 people aboard. Some similarities have been drawn with a Lion Air crash off the coast of Indonesia last year, in which a Boeing 737 Max also came down shortly after its departure.
Some experts and commentators have highlighted a new software anti-stalling system installed on the 737 Max designed to compensate for the aircraft's more powerful engines and different placement on the wings.
"The role of this air data sensor equipment and the way that this stability augmentation system works must remain a focus of attention," air safety specialist Young told RFI, pointing out that the potential lack of training for this system was a vital element.
A number of countries took action to ban the 737 Max from their skies, although the FAA resisted grounding the Boeing planes until Wednesday's announcement.
"Their decision is based on safety data, rather than what has been used by a number of countries, a phrase - 'an abundance of concern,'" said Young, who has worked on safety management for various airlines and as an accident investigator.
"I think what is not normal is the fact that so many states took very swift, unilateral action based on this idea of abundance of concern, and didn't wait for safety data," he added.
Grounding of aircraft is rare and there have only been a handful of examples since the beginning of the jet age, according to Young. Notably, the de Havilland Comet in 1954, the DC-10 in 1979 and the Boeing 787 Dreamliner in 2013.
Russia, Japan and Tunisia became the latest countries to ban the 737 Max, while the Indonesian government announced that it would send officials from its transport safety agency to help with Ethiopia's investigation. The Lion Air crash last October that killed all 189 on board shortly after take-off from Jakarta involved the same Boeing model.
Black box data recorders
Black boxes from flight ET302 arrived in Paris on Thursday and will be analysed by France's Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA). There are four main locations across the world specialising in analysis of flight data recorders - France, Germany, UK and US.
"They are one of the leading analysis centres for data recorders in the world," Young said of the Ethiopian authorities' decision to send the black boxes to Paris.
Young said the black boxes would hopefully reveal the communications between the pilots, the settings of all the plane's systems and monitoring data indicating how the plane reacted. This would be used to help build up a picture of what happened - any fault codes and how the flight deck reacted.