Boeing plans further changes to the software architecture of the 737 MAX flight-control system to address a flaw discovered after a test in June, according to two people briefed on the matter.
The redesign, first reported by the Seattle Times, involves using and receiving input from both flight control computers rather than one.
The move comes in response to an effort to address a problem discovered in June during a Federal Aviation Administration (FAA) simulator test.
This is on top of earlier announced changes to take input from both angle-of-attack sensors in the MCAS anti-stall system linked to two deadly crashes that led to a global grounding of the plane.
Boeing still hopes to complete the software redesign by the end of September to submit to the FAA for approval, the sources said.