As part of the work to return the Max to service, the company and regulators have scrutinized every aspect of the jet, uncovering new potential design flaws.
At the request of the Federal Aviation Administration, Boeing conducted an internal audit in December to determine whether it had accurately assessed the dangers of key systems given new assumptions about how long it might take pilots to respond to emergencies, according to a senior engineer at Boeing and three people familiar with the matter.
Among the most pressing issues discovered were previously unreported concerns with the wiring that helps control the tail of the Max.
The company is looking at whether two bundles of critical wiring are too close together and could cause a short circuit. A short in that area could lead to a crash if pilots did not respond correctly, the people said. Boeing is still trying to determine whether that scenario could actually occur on a flight and, if so, whether it would need to separate the wire bundles in the roughly 800 Max jets that have already been built. The company says that the fix, if needed, is relatively simple.
The company informed the F.A.A. about the potential vulnerability last month, and Boeing’s new chief executive discussed possible changes to the wiring on an internal conference call last week, according to one of the people and the Boeing engineer, who spoke on the condition of anonymity to discuss internal deliberations.