The Federal Aviation Administration (FAA) said Monday that it expects Boeing to propose a software fix to its 737 Max planes within the "coming weeks," saying that more time "is needed for additional work by Boeing."

“The FAA expects to receive Boeing’s final package of its software enhancement over the coming weeks for FAA approval. Time is needed for additional work by Boeing as the result of an ongoing review of the 737 MAX Flight Control System to ensure that Boeing has identified and appropriately addressed all pertinent issues," the FAA said in a statement.

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Boeing previously said it planned to propose a fix to the software by last week, according to Reuters.

The Boeing 737 Max’s Maneuvering Characteristics Augmentation System (MCAS), an automated flight control system, has come under scrutiny following two fatal crashes in recent months involving the jets.

Investigators believed the system was erroneously activated during a Lion Air flight in Indonesia last year, forcing the plane to dive down. The software is also thought to have played a role in an Ethiopian Airlines crash last month.

The FAA said in the statement Monday that it will "subject Boeing’s completed submission to a rigorous safety review."

"The FAA will not approve the software for installation until the agency is satisfied with the submission," the agency added.

Boeing 737 Max jets have been grounded in the U.S. and other major countries for several weeks.