Aviation regulators from around the world will meet on Thursday to decide when the grounded Boeing 737 Max will return to the skies.
The meeting, led by the US Federal Aviation Administration (FAA), could set out a timetable for when the aircraft can return to service.
The 737 Max was grounded in March following two crashes in five months which claimed the lives of 346 people.
Boeing has completed a software update for the jet which the FAA must approve.
The regulator said it would provide its safety analysis to delegates from 33 countries, including the UK, Europe and China, at the meeting in Texas.
The safety analysis will determine when the 737 Max can return to service in the US.
The FAA also said it “will provide safety experts to answer any questions participants have related to their respective decisions to return the fleet to service”.
Boeing has developed a software update for the Manoeuvring Characteristics Augmentation System (Mcas) on the 737 Max – a new feature on the jet designed to improve the handling of the plane and to stop it pitching up at too high an angle.
Mcas has been linked to both the Ethiopian Airlines crash in March, which killed 157 passengers and crew, and the Lion Air disaster in Indonesia at the end of October, in which 189 people perished.
The FAA is expected to conduct a certification flight in the coming weeks, which, if successful, means the 737 Max could return to flight in the US during the summer.
However, the executive chairman of the International Pilot Training Association, Captain Tilmann Gabriel, told the BBC that was rather unlikely: “The FAA current acting director general has made it very clear that he is not committing to October, which was the real date [for the reintroduction], but there is so much to do.
“The credibility of the FAA and Boeing is at stake here. I’m convinced that there is a fix found, but this has to be now properly introduced.
“The big thing is that the simulators had not anticipated the Mcas. Pilots didn’t know about it and if the authorities decide that all pilots have to be trained in a simulator that [could] cause a very big delay.”
It is also not clear when regulators outside the US in other countries will allow the plane back in the air.
China was the first country to ban the 737 Max from its skies following the Ethiopian Airlines crash. Other nations including the UK, Australia, New Zealand and the European Union soon followed suit.
The US was one of the last countries to ground the 737 Max in March following the Ethiopian Airlines crash. Southwest Airlines and American Airlines are the biggest operators of the 737 Max globally.
Another issue facing the FAA is whether to make pilot training on 737 Max simulators a requirement before the plane can return to service.
The FAA said it was “still under review”.
The New York Times recently reported that the simulators – which Boeing provides the software for – were not able to accurately replicate conditions similar to those which played a part in both the Ethiopians Airline and Lion Air disasters.
Boeing said it “has made corrections to the 737 Max simulator software and has provided additional information to device operators to ensure that the simulator experience is representative across different flight conditions”.
It added that it was working with both the manufacturers of the simulators and regulators “on these changes and improvements and to ensure that customer training is not disrupted”.
Meanwhile, the International Air Transport Association (IATA) will also hold a meeting on Thursday with airlines that have grounded the 737 Max.
Alexandre de Juniac, the IATA’s director general and chief executive, said the gathering was designed to assess what the airlines “expect from the manufacturer and from the regulatory authorities”.