Boeing admitted Sunday that it  knew well over a year before the first crash of a 737 MAX in Indonesia last October that a warning light linked to a key sensor on the 737 MAX wasn’t working on most of the airplanes, but it informed neither the Federal Aviation Administration (FAA) nor the airlines operating the jet about the problem until after that crash.

The warning light is significant because it warned of a malfunction in one of the jet’s Angle of Attack (AOA) sensors, a fault that began the sequence of events that led to both the Lion Air crash in October and the Ethiopian Airlines crash in March.

The alert worked only on planes flown by airlines that had bought a separate and optional AOA indicator added to the main flight display panel. Boeing disclosed the existence of the problem publicly only last week after a story in the Wall Street Journal. It disclosed its prior knowledge on Sunday only after a follow-up story.

Furthermore, even MAX operators like American Airlines that had bought the optional indicator were misinformed by Boeing last year after the Lion Air crash about how the warning light operates.

As Boeing deals with the crisis following the loss of 346 lives in two crashes and works to convince the FAA, the airlines and the public that the MAX should be allowed to fly again as early as next month, the lack of transparency and confusion is damaging Boeing’s credibility.

“The more and more we learn with each day, the more challenging it is to rebuild the trust,” said American Airlines Captain Dennis Tajer, spokesman for the Allied Pilots Association (APA). “This slow toxic drip of full disclosure only after full discovery … (has) got to stop if we are going to rebuild the trust that has been so deeply violated.”


Boeing said Sunday that its engineers discovered that the warning light wasn’t functioning, due to a software mistake, “in 2017, within several months after beginning 737 MAX deliveries” in May that year.

Boeing then conducted an internal review, which “determined that the absence of the AOA Disagree alert did not adversely impact airplane safety or operation.”

“Neither the (optional) angle of attack indicator nor the AOA Disagree alert are necessary for the safe operation of the airplane,” Boeing said in the statement.

Its review concluded “the existing functionality was acceptable,” Boeing said, adding that it decided that  the warning light could be made functional later by de-linking it from the optional display indicator during “the next planned display system software update.”

That update was never done before the MAX fleet was grounded in March following the second crash.

Boeing said that it wasn’t until after the Lion Air crash that it “informed the FAA that Boeing engineers had identified the software issue in 2017.”


Its statement seemed to point blame at an unnamed supplier when it stated that the problem was located in “the software delivered to Boeing.”

It also made a point of asserting that “senior company leadership was not involved in the review and first became aware of this issue in the aftermath of the Lion Air accident”

The FAA, in a separate statement Sunday, said that following the disclosure by Boeing in November, its Corrective Action Review Board “determined the issue to be ‘low risk'” and decided it could be dealt with as part of Boeing’s software update announced after the Lion Air crash and still in the works.

The FAA statement then adds: “However, Boeing’s timely or earlier communication with the operators would have have helped to reduce or eliminate possible confusion.”

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Boeing did not inform the airlines, the pilots and the public until April 29, six weeks after the second crash. Even then, it didn’t mention until Sunday that it had known about the warning light issue since mid-2017.

The warning light, standard on the MAX and included in the pilot manuals, is designed to light up if there’s a disagreement between the two sensors on either side of the plane’s nose that measure the jet’s angle of attack — the angle between the oncoming air flow and the airplane’s wing.


If it had been working, the warning light would have lit up on the fatal flights of both the Lion Air and Ethiopian jets. Though it might have provided the pilots an extra early clue as to what was going wrong, it likely wouldn’t have made a big difference in either crash scenario.

The AOA alert wouldn’t have helped the Lion Air pilots understand their situation any better because they were also unaware of the new MAX flight control system — called Maneuvering Characteristics Augmentation System, or MCAS — and how it was activated. MCAS was not in the pilot manual.

The Ethiopian pilots, who after the previous crash would have been keenly aware of MCAS, seem to have realized that system was the problem reasonably quickly and tried to follow Boeing’s recommended checklist of procedures to handle it, though they still were not able to control the plane.

Tajer said that even though his airline had installed the optional feature and so had a functional warning light, American Airlines pilots are still unhappy at what he described as newly discovered “misdirection”  by Boeing.

In a Nov. 27, 2018, meeting following the Lion Air crash, Boeing offered American Airlines pilots reassurance that the Lion Air scenario couldn’t happen to them because they had this warning light.

The two AOA sensors on the Lion Air jet disagreed by a large margin, about 20 degrees, throughout the flight and even while the jet taxied on the ground before takeoff when both readings should have been zero. Tajer said the American pilots were told in the meeting that on the flight deck of their 737 MAXs, the AOA disagree light would have lit up on the ground and so, because that’s a “no-go item,” the plane wouldn’t even have taken off.


However, Tajer said that within the last two to three weeks, “we are now learning that, unlike Boeing told us in November, the warning light actually is inhibited on the ground.”

“We are being told by Boeing that the AOA Disagree Alert … is inhibited until 400 feet above ground level,” he said Sunday. “We are currently awaiting written confirmation of this AOA Disagree Alert limitation as it is not detailed in any 737 flight crew manual.”

“Having any equipment detailed in the manual that doesn’t actually exist …. has no place in aviation. There’s no fiction in flight, just the facts,” Tajer added. “Literally, lives count on that.”