The Federal Aviation Administration tells the BBC it didn't have the information needed to ground the planes.Read more
Boeing 737 Max 8
The FAA is working with the aviation industry to ensure the 737 Max is safe enough to fly again.
BBC Radio 4
Aviation regulators from around the world will meet later today to decide when the grounded Boeing 737 Max can return to the skies.
The meeting, led by the US Federal Aviation Administration (FAA), could set out a timetable for the aircraft - grounded in March following two crashes in five months which claimed the lives of 346 people - to return to service.
The executive chairman of the International Pilot Training Association, Captain Tilmann Gabriel, has been speaking to BBC Radio 4 Today's Programme.
"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."
Read the BBC's story here.
Nine global aviation regulators, including from from China, the EU, Canada and Brazil, will meet on Thursday to review Boeing's application to get the Max airplane model flying again, the Financial Times has reported.
In March, Boeing grounded its entire global fleet of 737 Max aircraft after two fatal crashes within five months.
The US firm said last week it had completed the development of a software update for its 737 Max plane.
The Federal Aviation Administration has said it would hold a meeting on 23 May with air regulators from around the world to provide an update on reviews of Boeing's software fix and new pilot training.
American Airlines pilots confronted Boeing about concerns regarding the Boeing 737 Max, the model that crashed in Ethiopia on March 10, US media has reported.
A meeting took place in November last year following a crash in Indonesia that killed 189 people.
Pilots said they hadn't been fully informed about the new anti-stall system, which investigators say may have caused the crashes.
Boeing promised to make changes to software but this was still in progress when the Ethiopian Airlines plane crashed and killed all 157 people on board.
The 737 Max is currently grounded worldwide.