Last year, inspectors with the Federal Aviation Administration discovered Boeing deactivated a signal designed to advise the cockpit crew of a malfunctioning of the MCAS system, the source said.
The inspectors were in charge of monitoring Southwest Airlines, the biggest user of 737 MAX planes, with a fleet of 34 of them at the time, the source said.
Before the Lion Air crash, which killed all 189 people on board, signals “were depicted as operable by Boeing on all MAX aircraft” regardless of whether the cockpit crew thought they had them turned on or off, said a Southwest spokeswoman.
She said after the accident, Boeing told Southwest the signals were “turned off unless they were specifically designated as being turned on” – prompting the airline to choose that option for all its aircraft.
It was at that point inspectors learned Boeing decided to make the malfunction alert an optional extra costing more money – and deactivated the signal on all 737 MAX delivered to Southwest without telling the airline.
They considered recommending grounding the planes as they explored whether pilots flying the aircraft needed additional training about the alerts, said the source.
They decided against that – but never passed details of the discussions to higher-ranking officials in the FAA, the source said, confirming a story in The Wall Street Journal.