FILE PHOTO: Boeing 737 MAX aircraft are parked at a Boeing production facility in Renton, Washington, U.S., March 11, 2019. REUTERS/David Ryder

WASHINGTON (Reuters) - The United States expects it will take months before a software fix for Boeing 737 Max planes is complete, the acting administrator of the Federal Aviation Administration said on Wednesday, adding that he does not know how long the country’s grounding of the aircraft will last.

Acting administrator Dan Elwell told a conference call with reporters that the “black boxes” from Sunday’s Ethiopian Airlines plane crash are headed to France later on Wednesday.