Boeing is repairing a second software problem on its grounded 737 MAX airliners while working on a patch to an anti-stall system linked to the crash of two of its planes.

The aerospace giant has been reviewing software on its single-aisle 737 MAX in the wake of last year’s Lion Air crash in Indonesia and the downing of an Ethiopian Airlines plane last month, both of which killed all passengers on board.

The crashes, which implicated the plane's Maneuvering Characteristics Augmentation System, or MCAS, led the Federal Aviation Administration to follow its international counterparts in grounding Boeing’s 737 MAX fleet. Boeing said it has been working with the FAA and its customers on a software update to prevent future accidents.

In its statement, the company said that as part of its review, “We have identified an aspect of the software, unrelated to MCAS, that will also be addressed as part of this software update," according to reports in the Wall Street Journal and other publications. “We are taking steps to thoroughly address this relatively minor issue and already have the solution in work to do that."

Earlier this week, the company decided to extend the timeline for delivering the software upgrade, which the FAA now expects to receive “over the coming weeks.”

Boeing acknowledged on Thursday that the MCAS system was partly to blame for the two accidents involving the 737 MAX, the company's latest version of a single-aisle jetliner introduced in 1967 that has become one of the world's most widely flown planes.

The company said its engineers were “working tirelessly” with the FAA on a patch to prevent future issues with the anti-stall system.

“We’re taking a comprehensive, disciplined approach, and taking the time, to get the software update right,” Boeing CEO Dennis Muilenburg said in a statement Thursday. “We’re nearing completion and anticipate its certification and implementation on the 737 MAX fleet worldwide in the weeks ahead.”

The Trump administration decided to ground the 737 MAX fleet after flight data from the Ethiopian Airlines jet showed choppy ascents and descents during takeoff similar to those that occurred before the Lion Air jet crashed.

[Related: Ethiopia Airlines crew not at fault for Boeing 737 MAX 8 crash, preliminary investigation finds]