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, two people briefed on the matter said late on Thursday. 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.

Boeing 737 MAX airplanes are stored in an area adjacent to Boeing Field, on June 27, 2019 in Seattle, Washington. After a pair of crashes, the 737 MAX has been grounded by the FAA and other aviation agencies since March, 13, 2019. The FAA has reportedly found a new potential flaw in the Boeing 737 Max software update that was designed to improve safety. Stephen Brashear | Getty Images News | Getty Images

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. For decades, 737 models have used only one of the flight control computers for each flight, with the system switching to the other computer on the following flight, according to people familiar with the plane's design. The FAA said in June that it had identified a new risk that would need to be addressed before the plane could be ungrounded.