TO THE BOEING COMPANY: Continue the certification process for the design enhancement for mid exit door plugs to ensure that, once the design enhancement is certified, all applicable newly manufactured airplanes are equipped with the enhancement.
Safety Issue and Context
This report discusses the January 5, 2024, accident involving a Boeing 737 9 airplane operated by Alaska Airlines that experienced an in-flight separation of the left mid exit door (MED) plug and rapid depressurization during climb after takeoff from Portland International Airport. One flight attendant and 7 passengers received minor injuries; the captain, the first officer, 3 flight attendants, and 164 passengers were uninjured; and the airplane sustained substantial damage.
Safety issues identified in this report include the circumstances of the airplane’s manufacture at Boeing Commercial Airplanes’ Renton, Washington, manufacturing facility that led to opening of the left MED plug without the required removal record to ensure that removed bolts and attachment hardware were properly replaced; the complexity of Boeing’s business process instruction (BPI) for parts removals and its inadequate training of manufacturing personnel; Boeing’s ineffective change management related to workforce experience level decreases; Boeing’s ineffective corrective actions and the Federal Aviation Administration’s (FAA) ineffective oversight that allowed the persistence of issues with Boeing’s BPI for parts removals; the need for Boeing to improve quality escape mitigation strategies and continue development of its safety management system; the need for hands on emergency oxygen mask training for flight crews; the need for portable oxygen bottle design standards review; the need for effective operator procedures and 25 hour cockpit voice recorder (CVR) installations and retrofits to prevent the loss of CVR audio; and the safety benefits of using child restraint systems for children under the age of 2 years.
As a result of this investigation, the National Transportation Safety Board makes 11 recommendations to the FAA and 8 recommendations to The Boeing Company, and reiterates 4 safety recommendations to the FAA and 1 safety recommendation to Airlines for America, the National Air Carrier Association, and the Regional Airline Association.
Response History
September 30, 2025 · Recipient Response · Boeing Company
-From Stella Weidner, Director, Product Safety: As documented in Boeing’s submission and the NTSB final report, Boeing is developing design enhancements to the Mid Exit Door (MED) plug consisting of secondary retention devices that inhibit vertical movement of the MED plug and lanyards that ensure that the primary MED plug retention hardware remains in place. Boeing has communicated progress on incorporation of these design enhancements to operators of the affected 737-9 fleet via Fleet Team Digest (FTD) article (737MAX-FTD-53-24002).
The FTD article includes expected certification completion and incorporation timing of these enhancements on a production 737-9 airplane in December 2025 and all newly delivered 737-9 airplanes beginning in January 2026. Any updates to expected incorporation dates will be provided via revision to the FTD article on this topic. A copy of 737MAX-FTD-53-24002 has been provided to the NTSB.
July 10, 2025 · NTSB Correspondence · Boeing Company
The NTSB is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant events in the other modes of transportation—railroad, transit, highway, marine, pipeline, and commercial space. We determine the probable causes of the accidents and events we investigate and issue safety recommendations aimed at preventing future occurrences. In addition, we conduct transportation safety research studies and offer information and other assistance to family members and survivors for each accident or event we investigate.
We also serve as the appellate authority for enforcement actions involving aviation and mariner certificates issued by the Federal Aviation Administration (FAA) and US Coast Guard, and we adjudicate appeals of civil penalty actions taken by the FAA.
We are providing the following information to urge The Boeing Company, Boeing Commercial Airplanes’ business unit, to act on the safety recommendations in this letter because we believe your organization can help reduce the risk of future accidents.
This letter also includes information about our June 24, 2025, report, In-Flight Separation of Left Mid Exit Door Plug, Alaska Airlines Flight 1282, Boeing 737-9, N704AL, Portland, Oregon, January 5, 2024, AIR-25-04. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at
As a result of this investigation, we identified the following safety issues:
• The incomplete closure of the accident airplane’s left mid exit door (MED) plug (with missing securing bolts and hardware) after it had been opened to facilitate rework during the manufacturing process;
• The need for the completion of your MED plug design enhancement to help ensure the complete closure of an MED plug following opening or removal;
• The lack of clarity, conciseness, and ease of use of Business Process Instruction (BPI) “Perform Part or Assembly Removal” needed for it to be an effective tool for manufacturing personnel to consistently and correctly determine when and how to generate a removal record;
• The inability of your unstructured and undocumented on-the-job training to adequately prepare door team personnel with limited exposure to nonroutine tasks to correctly perform the process for opening an MED plug, including generating the required removal record, and to track trainee progress to support future data analysis;
• The ineffectiveness of your corrective actions to address the persistent deficiencies with BPI “Perform Part or Assembly Removal” and other production process inconsistencies identified in the investigation; and
• The inadequacy of your quality escape guidance to address controls for human error.
Accordingly, the NTSB makes the following safety recommendations to Boeing. Additional information regarding these recommendations can be found in the noted sections of the report.
Continue the certification process for the design enhancement for MED plugs to ensure that, once the design enhancement is certified, all applicable newly manufactured airplanes are equipped with the enhancement. (A-25-26) (See sections 1.12.2.7 and 2.3.2.)
Once the design enhancement for MED plugs is certified, issue a service bulletin to address retrofitting in-service MED plug equipped airplanes with the design enhancement. (A-25-27) (See sections 1.12.2.7 and 2.3.2.)
Apply your updated safety risk management process to current and future revisions to BPI “Perform Part or Assembly Removal” to ensure that it provides clear and concise guidance for determining when a removal record is needed. (A-25-28) (See sections 1.11.2.1.1, 1.11.2.3.3, and 2.3.1.1.)
Develop recurrent training on BPI “Perform Part or Assembly Removal” for Boeing manufacturing personnel that emphasizes the importance of removal records for product safety, prepares personnel to consistently and correctly determine when a removal record is needed, and ensures that a removal record is generated when required. (A 25-29) (See sections 1.11.2.1.1, 1.11.2.3.3, and 2.3.1.1.)
Develop a structured on-the-job training program that identifies and defines tasks necessary for manufacturing personnel to be considered fully qualified in their job series and includes a grading system for trainers and trainees to track progress and determine competence. (A-25-30) (See sections 1.11.2.2.1, 1.11.2.2.2, and 2.3.1.2.)
Document and archive the results of training provided and received as part of the program recommended in Safety Recommendation A-25-30 to support future data analysis. (A-25-31) (See sections 1.11.2.2.1, 1.11.2.2.2, and 2.3.1.2.)
Revise your safety risk management process to ensure that it 1) identifies the root causes of manufacturing process compliance issues, like the persistent deficiencies with BPI “Perform Part or Assembly Removal” and other production process inconsistencies identified in this investigation, and 2) evaluates the effectiveness of corrective actions. (A 25-32) (See sections 1.11.2.3.3 and 2.4.2.1.)
As you integrate your quality management system and safety management system, develop a process that can identify escapes that result from human error, assess them using a system specifically designed to identify factors that contribute to such errors, and implement effective mitigation strategies. (A 25-33) (See sections 1.11.2.3.1, 1.11.2.3.2, 1.11.2.3.3, 2.4, and 2.5.)
The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days of the date of this letter, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendation by number (Safety Recommendations A-25-26 through -33). We encourage you to submit your response to ExecutiveSecretariat@ntsb.gov. For your convenience, please refer to additional guidance on responding to our safety recommendations on our website.
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All communications regarding safety recommendations are stored by the NTSB and viewable by the public. Please do not send privileged or confidential communications in response to these recommendations. Responses marked as confidential or privileged (or similar designations) will be considered nonresponsive. In the likely event that your company uses auto generated and/or preformatted confidentiality statements on letterhead or outgoing e-mails, please include a statement in your letter indicating that the information can be publicly released. If you have concerns about this protocol, please contact us at ExecutiveSecretariat@ntsb.gov.
From the Aviation Investigation Report AIR-25-04 "In-Flight Separation of Left Mid Exit Door Plug, Alaska Airlines Flight 1282, Boeing 737 9, N704AL Portland, Oregon January 5, 2024," published on July 10, 2025
1.12.2.7 Ongoing Work on Mid Exit Door Plug Design Enhancement Certification
After the accident, Boeing worked with Spirit AeroSystems (which owned the MED plug engineering design) to develop a design enhancement to add two secondary retention devices to prevent an MED plug from moving upward in the event that the vertical movement arrestor bolts and upper guide track bolts were not installed. The retention devices would also prevent the sidewall panels from being installed unless the devices were engaged. The design enhancement also added lanyards to the vertical movement arrestor bolts and upper guide track bolts so that they would remain hanging on the frame or plug when removed, providing a visual indication when the bolt