(WASHINGTON) -- The acting administrator of the Federal Aviation Administration said Thursday morning that he didn't know when Boeing 737 Max 8 or 9 aircraft would fly again in U.S. airspace.
"We don't know how long the planes will be grounded," Daniel Elwell told ABC News Chief Anchor George Stephanopoulos in an interview.
The black boxes from Ethiopian Airlines Flight 302, which crashed about six minutes after taking off on Sunday from Addis Ababa Bole International Airport in Ethiopia's capital, killing all 157 people aboard, have arrived in France and could provide initial data by the end of the day, Elwell added.
The raw flight data initially available on Sunday and Monday didn't match that of the Boeing 737 Max that crashed in October in Indonesia, killing all 189 people on board.
But after the data were further examined -- a joint effort by Boeing, the satellite data provider and the National Transportation Safety Board -- similarities emerged, Elwell said.
"When we could see the refined data," Elwell told Stephanopoulos, "it matched too closely to the Lion Air trajectory to figure that they weren't similar."
President Donald Trump on Wednesday ordered all 737 Max 8 and 9 jets in the U.S. grounded, joining Ethiopia, Indonesia, China and European Union.
A proposed software fix for the 737 is "almost complete," Elwell said.
"We expect by the end of this month all the testing will be complete, and we will authorize implementation of the fix," Elwell added.
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