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   A year before the first crash of a 737 MAX, Boeing was aware of software   
   problems with the plane. Boeing admitted on Sunday that a few months after the   
   delivery of the 737 MAX in May 2017, it was discovered that a warning system   
   in the cockpits was not working properly.   
       
   The AOA Disagree Alert only appeared to work in combination with another   
   optional function, the AOA indicator. From its own research, Boeing concluded   
   that the non-working safety option did not mean a deterioration of flight   
   safety.   
       
   The American aviation authority FAA was not informed until a week after the   
   first accident. The FAA subsequently issued an Airworthiness Directive (AD).   
       
   The 737 MAX airplanes have been on the ground worldwide since mid-March. This   
   is because of two fatal aircraft accidents in a short time, in Indonesia with   
   a Lion Air aircraft and in Ethiopia with an aircraft from Ethiopian Airlines.   
   They were found to be caused by the MCAS safety system that repeatedly pressed   
   down the nose due to a malfunctioning Angle of Attack (AOA) sensor.   
       
   It is not clear whether specifically the non-functioning AOA Disagree Alert   
   also played a role in the crashes. The software update that Boeing is   
   currently working on does ensure that the AOA Disagree Alert becomes a   
   standard option on the 737 MAX. The Angle of Attack indicator remains optional.   
       
   Read the full Boeing statement below:   
       
   Boeing Statement on AOA Disagree Alert On every airplane delivered to our   
   customers, including the MAX, all flight data and information needed to safely   
   operate the aircraft is provided in the flight deck on the primary flight deck   
   displays. This information is provided full-time in the pilots' primary field   
   of view, and it always has been.   
       
   Air speed, attitude, altitude, vertical speed, heading and engine power   
   settings are the primary parameters the flight crews use to safely operate the   
   airplane in normal flight. Stick shaker and the pitch limit indicator are the   
   primary features used for the operation of the airplane at elevated angles of   
   attack. All recommended pilot actions, checklists, and training are based upon   
   these primary indicators. Neither the angle of attack indicator nor the AOA   
   Disagree alert are necessary for the safe operation of the airplane. They   
   provide supplemental information only, and have never been considered safety   
   features on commercial jet transport airplanes.   
       
   The Boeing design requirements for the 737 MAX included the AOA Disagree alert   
   as a standard, standalone feature, in keeping with Boeing's fundamental design   
   philosophy of retaining commonality with the 737NG. In 2017, within several   
   months after beginning 737 MAX deliveries, engineers at Boeing identified that   
   the 737 MAX display system software did not correctly meet the AOA Disagree   
   alert requirements. The software delivered to Boeing linked the AOA Disagree   
   alert to the AOA indicator, which is an optional feature on the MAX and the   
   NG. Accordingly, the software activated the AOA Disagree alert only if an   
   airline opted for the AOA indicator.   
       
   When the discrepancy between the requirements and the software was identified,   
   Boeing followed its standard process for determining the appropriate   
   resolution of such issues. That review, which involved multiple company   
   subject matter experts, determined that the absence of the AOA Disagree alert   
   did not adversely impact airplane safety or operation. Accordingly, the review   
   concluded, the existing functionality was acceptable until the alert and the   
   indicator could be delinked in the next planned display system software   
   update. Senior company leadership was not involved in the review and first   
   became aware of this issue in the aftermath of the Lion Air accident.   
       
   Approximately a week after the Lion Air accident, on November 6, 2018, Boeing   
   issued an Operations Manual Bulletin (OMB), which was followed a day later by   
   the FAA's issuance of an Airworthiness Directive (AD). In identifying the AOA   
   Disagree alert as one among a number of indications that could result from   
   erroneous AOA, both the OMB and the AD described the AOA Disagree alert   
   feature as available only if the AOA indicator option is installed.   
       
   Boeing discussed the status of the AOA Disagree alert with the FAA in the wake   
   of the Lion Air accident. At that time, Boeing informed the FAA that Boeing   
   engineers had identified the software issue in 2017 and had determined per   
   Boeing's standard process that the issue did not adversely impact airplane   
   safety or operation. In December 2018, Boeing convened a Safety Review Board   
   (SRB) to consider again whether the absence of the AOA Disagree alert from   
   certain 737 MAX flight displays presented a safety issue. That SRB confirmed   
   Boeing's prior conclusion that it did not. Boeing shared this conclusion and   
   the supporting SRB analysis with the FAA.   
       
   Boeing is issuing a display system software update, to implement the AOA   
   Disagree alert as a standard, standalone feature before the MAX returns to   
   service. When the MAX returns to service, all MAX production aircraft will   
   have an activated and operable AOA Disagree alert and an optional angle of   
   attack indicator. All customers with previously delivered MAX airplanes will   
   have the ability to activate the AOA Disagree alert.   
      
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