After discovering a problem in 2017 with a cockpit warning light on the 737 MAX, Boeing decided it would defer an update to fix the issue until 2020, officials said Friday.

Even as it continued delivering MAX airplanes to customers, Boeing had kept quiet the details of the problem, which prevented a light from warning pilots when there was disagreement between the plane’s angle-of-attack sensors. Those sensors are now suspected of playing a role in two MAX crashes.

The company didn’t disclose the issue to the Federal Aviation Administration (FAA) until after a 737 MAX crash in Indonesia last year, something that frustrated FAA leadership. Now, leaders with a transportation committee in the U.S. House said they have obtained information about the initial plan to fix the issue in 2020. They have sent letters to Boeing, the FAA and supplier United Technologies requesting documents around the problematic alert.

“An important part of the Committee’s investigation is finding out what Boeing knew, when the company knew it and who it informed,” said Rep. Rick Larsen, a Washington state Democrat who leads the aviation subcommittee. “I have questions about the decision to not deem the AOA Disagree alert as safety critical and I am concerned it took Boeing so long to report this defective feature to the FAA and its customers.”

Boeing has said that its engineers discovered that the warning light wasn’t functioning in 2017, but the company concluded that the issue did not adversely impact the safety or operation of the plane. In a statement Friday, the company said it determined that it was acceptable to wait to modify the system software on its next planned display system update, which was scheduled for the rollout of the 737 MAX 10 in 2020.

“We fell short in the implementation of the AoA Disagree alert and are taking steps to address these issues so they do not occur again,” Boeing said.


The warning light, which is 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.

At the time of the crashes, the alert worked only on planes flown by airlines that had bought a different indicator added to the main flight-display panel. Lion Air and Ethiopian Airlines did not have those packages.


If it had been working, the warning light would have lit up on the fatal flights of both the Lion Air and Ethiopian jets. It’s not clear that it would have made a difference, as Lion Air pilots were unaware of the MAX’s new automated maneuvering system that pushed the plane’s nose down in response to the erroneous angle-of-attack data.

With knowledge of the overall system in the wake of the Lion Air crash, the Ethiopian pilots might have benefited from the information, but a preliminary report suggests they were ultimately able to diagnose the problem. They still weren’t able to maintain control of the plane.

Dan Elwell, the head of the FAA, has expressed concern that Boeing took 13 months to inform the FAA about the problematic disagree light, but he has also endorsed Boeing’s perspective that the light wasn’t a safety-critical issue. FAA leaders characterized it as an advisory light for the sake of maintenance, and Elwell told lawmakers there are no actions that pilots are to take when a disagree light engages.

At a hearing before a House committee investigating issues around the 737 MAX last month, Elwell encouraged members of Congress not to focus so much attention on the light.


“Don’t make something that isn’t a critical safety item a critical safety item, because there’s enough critical safety items for us to focus on,” he said.

The Aviation Subcommittee of the House Committee on Transportation and Infrastructure is scheduled to hold a second hearing on the 737 MAX on June 19.