MAX 9s Stay Grounded As Boeing Revises Inspection Requirements


Boeing 737 MAX 9s will remain out of service longer than initially thought while Boeing rethinks inspection requirements for the 171 aircraft in service. The FAA has ordered Boeing to revise inspection directions for Boeing 737 MAX 9 optional emergency exit plugs after it got “feedback” on the first set of instructions. “The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service,” the agency said in an X post accompanying the following statement:

Every Boeing 737-9 Max with a plug door will remain grounded until the FAA finds each can safely return to operation. To begin this process, Boeing must provide instructions to operators for inspections and maintenance. Boeing offered an initial version of instructions [Jan. 8] which they are now revising because of feedback received in response. Upon receiving the revised version of instructions from Boeing the FAA will conduct a thorough review.

Meanwhile Boeing held a company-wide safety meeting Jan. 9 in which an emotional CEO David Calhoun urged employees to double down on safety. “These things matter,” he said. Calhoun also pledged full cooperation with authorities and to apologize for whatever missteps the company may have made.

Russ Niles
Russ Niles is Editor-in-Chief of AVweb. He has been a pilot for 30 years and joined AVweb 22 years ago. He and his wife Marni live in southern British Columbia where they also operate a small winery.


  1. Yay, someone with more common sense than Alaska who said, “Huh, all the other doors still seem to be there, let’s fly!”

  2. Too many cooks spoil the broth or not enough duct tape?

    I get it, the making of Boeing 737 MAX 9s is complex, with multi-location production sites adding to the complexity. It all starts in Kansas before making its way to Boeing’s factory in Seattle via train. In Renton, WA, they temporarily remove the door plug panel using the port to bring in seats and other components, perhaps allowing for dings, IDK, then reinstall the door plug making sure everything is just right including pressurizing the hull for quality assurance. (as reported by Reuters, January 9, 202410:13 AM MST)

    However, despite the meticulous process, errors occur. A door plug leaves one perfectly good airplane, and wham! 171 aircraft get grounded. More than the AVweb commentariat expected, I think. United Airlines and Alaska Airlines have a considerable number out of service– 79 and 65 planes, respectively. The caution extends to international carriers as well, with 56 aircraft awaiting resolution. I trust that the problem will be solved.

    • This is just the early stages of what is going to be a continuing rollout of screw ups by Boeing. It took a long time to get here. I would normally say it would take a long time to get out, but, they’re not going to, they can’t. It’s too entrenched. I know what the issue is here, we all do. However, if I put it down in print I’m sure to get deleted. So, let’s just all stick our heads in the sand and it will all go away, right? Who knows? This post may get deleted also.

    • The assembly of a 737 is too complex?!
      Airbus are the world champions of convoluted, displaced, geographically nonsensical distributed manufacturing processes spanning a half dozen countries, and they seem to have gotten in pretty much right. And Boeing can’t do this with an 80% North American supply chain?

  3. Y’know, that’s another good thing about building your own aircraft: you are also your own QC inspector, for good or ill. Your commitment to safety, construction, and inspection procedures is enhanced by the specter of that impending first flight. It tends to focus the mind on doing it right. Too bad Boeing can’t require everyone involved in the assembly of a new airliner to go along on one of the test/acceptance flights …

    • Cost of the employees shows up on the CFO’s spreadsheet. Cost of door, while real and huge, does not show up on the spreadsheet.

    • Here, here… having a physical, vested interest always makes one pay close attention to every detail.

    • I am not a A&P/IA or a experimental builder, but I have been known to ask the one who has just done service to my aircraft, especially an annual, to accompany me on my first test flight (usually in the pattern) after said service. I ask them to pay close attention and if anything seems “off” or sounds odd, to immediately inform me – so far, so good!

  4. There must be more to this. Another factor. The door plug cannot move UP without first moving INWARD. Why? Because of those 12 pinned stop castings. So loose or missing bolts alone can’t allow the door to become dislodged. So what can move the door inward to disengage those pins? The pressure is higher inside the plane right? But is it always that way? Let’s say the plane descends from 35k ft down thru 6k ft. Is there a delay in venting the cabin’s now lower-than-outside pressure? If there is such a pressure reversal that could make the door move inward (if the bolts are missing) dislodging the stop pins. Just a theory!

    • That’s not what happened. The Alaska airplane was climbing when the door opened. The 12 door stops don’t have pins, they are just flat pads. Cabin differential pressure will increase the friction on those pads, making it harder but not impossible to move the door up. The airplane was at 15,000′ altitude, so there is less pressure than at cruise. If any bolts were installed, the door would not move up. All it took was a little turbulence.

      • Hey Russ!…can we get a like button on this thing?
        The mechanics of how this door was able to pop out is something I’ve wondered about from the beginning and I’ve never heard it explained until now. Thank you!

      • Thanks for the correction. I’ve looked hard for a side view of the door plug to verify pads, and not pins. But you’re not the first to point this out. The silvery-looking hardware at the center of the PLUG stops are screws to adjust the pads for door fit. Just like threaded feet to keep a refridgerator from rocking. HOWEVER, even if the stops are not pinned, it still means the door has to rise upwards to disengage the stops and the two rollers at the top. What combination of missing lock bolts or loose brackets can cause the door rise? Could a missing bottom spring stop bolt and a missing roller lock bolt at the top, same side, could cause enough angular force to dislodge the whole thing? Regarding the air pressure bbgun06, my point was not that the plug dislodging from reverse air pressure happened on THAT flight, but that reversed air pressure could have caused misalignment on PREVIOUS flights, setting up the failure for the climb out. I don’t know how quickly cabin pressure valves respond to descents. Cabin pressure has to be reversed to go ambient at some point before landing, right?

  5. The solution is sensors for every bolt and attachment device on the airplane. If something breaks or loosens – the “Fasten Seat Belt” light illuminates and the Boeing stock price warning light comes on.

  6. If you select employees by any criteria other than competence, you will get less competence. Boeing and Spirit have both been boasting about hiring people by skin shade. Almost 50% of Boeing’s new hires in 2022 were “people of color.”
    Perhaps if David Calhoun had not “doubled down” on diversity, he wouldn’t have to plead with his employees to “double down” on doing their jobs right.

    • Racial Distribution at Boeing:

      White 59.0%
      Hispanic or Latino 14.2%
      Asian 12.7%
      Black or African American 9.0%
      Other 5.1%
      Boeing is a male-dominated company. 73% of Boeing employees are male and 27% of Boeing employees are female.

      • There are a lot of reasons for the male dominance at Boeing than prejudice. For example, women have been flying for the major airlines for decades and the airlines are more than happy to hire them if they want the job and are even remotely qualified. That being said women represent a very small percentage of airline pilots. Why is that?

    • The Racial/Ethnic distribution of the Army:
      White, Not Hispanic: 53.6%,
      Black, Not Hispanic: 20.3%,
      Hispanic: 17.6%,
      Asian or Pacific Islander: 6.9%,
      American Indian or Alaskan Native: 0.9%, and
      Unknown/Other: 0.8%.
      Males: 84.3%

    • The Racial/Ethnic distribution of the U.S.:
      White, 59.3%
      Hispanic and Latino, 18.9%
      Black, 12.6%
      Asian, 5.9%
      Two or more races, 2.3%
      American Indian or Alaska Native, 0.7%
      Some other race, 0.5%
      Native Hawaiian or Other Pacific Islander, 0.2%
      Females: 50.5 percent compare to 49.5 percent male population.

      The employment demographics are in somewhat in balance. It is preposterous to lay the blame for increasing manufacturing errors on DEI practices. Manufacturing errors are multifaceted issues that require a thorough investigation into operational processes, quality assurance, and training protocols

    • Spirit AeroSystems demographics.

      76% of Spirit AeroSystems employees are male and 24% of Spirit AeroSystems employees are female. The most common race/ethnicity at Spirit AeroSystems is White. 69% of employees at Spirit AeroSystems are White.

    • Boeing has been making efforts to increase diversity in its workforce. According to a report by Boeing, in 2022, the company exceeded its goal of achieving diverse interview slates for at least 90% of manager and executive openings, with 92% of interview slates being diverse, resulting in 47% diverse new hires.

  7. I learned to fly in a metal spar J3 when every FBO had J3’s, Champs, T-craft, or maybe a Luscombes,not just Cessnas. The J3’s were built in Loch Haven and everything was inexpensive but correct. Piper moved to Florida and built Traumahawks with much cheaper labor. Then I flew Cessnas. Cheap labor does know what the corporate culture is no matter how many smarmy speeches are written by the PA types and read by the CEO.

    Oh, the Piper Museum in Loch Haven is “temporarily closed”.

  8. Asking knowledgeable a/c assemblers and a&p people; are locknuts used in those bolts? I’m guessing aluminum expands and contracts with varying temperatures aircraft encounter from deserts to minus 60F at cruising altitude so keeping fasteners from loosening is a mechanical engineering exercise.

    • I’m not an assembler, but the photo showing the loose bolt also shows the properly secured locking bolt. The popular photo shows a round bracket with two attachment bolts on the right of the shot – one of those bolts is backed out.

      That bolt is NOT the suspect fastener, it is a separate issue!

      The bolt which holds the spring in compression is the one with the castellated nut, properly fastened in the pic. (The spring itself can be seen in the lower left of the shot.)

      The upper part of the plug has rollers which slide into channels. A lock bolt runs perpendicular through each channel, preventing the roller from sliding down. All four bolts undergo a shearing load; there is virtually no force against the securing nuts.

      This looks hugely like a case of NOT installing the hardware in the first place, not a material or design failure.

  9. As per Boeing, “something is rotten in the state of Denmark” according to the Bard and this fits for the folks in Renton.

  10. Quality control is an obligation of management. Worker performance should be monitored by management. Claiming that Boeing can’t get its act together because they hire the wrong “skin shade” is an absurd conclusion for a company that can’t ensure that the fasteners on its airplanes are tight.

    Toyota builds its cars in Alabama, Texas, and Mississippi. They hire workers from the same pool of applicants (skin color and all) and yet they seem to get the bolts tight on its cars. Maybe it has something to do with manufacturing methods and policies that emphasize product quality.

  11. No one set of physical characteristics lends anyone to be more or less capable as a human being. For now, there’s not enough information to determine that any one person is at fault for the misinstalled or otherwise defectively installed door plug. Let the investigation take place first.

    I remember as teenager, while working on a SNJ-2, I asked my boss how the fuselage welds looked so perfect. He said, “women did that, grandmothers, mothers, the girl next door and all learned to weld”. Wow. For the rest of the summer I would look at these beautiful welds imagining my mom doing something like that.

    • And the grandmothers, mothers, and girls next door probably had their minds on their grandsons, sons, and fiancees when they made those beautiful welds.

  12. I would be very interested in reading the maintenance logs from the previous times when the plane was examined following the pressure anomaly warnings in flight. Was the door plug examined, or did they concentrate on other areas such as the operating door seals or the pressure control system on the rear bulkhead? Also, were the inspections done on a quick turn overnight maintenance session or during a more comprehensive airframe inspection interval? If Boeing is having to revise its inspection instructions, I suspect that the mechanics did not have the necessary data to know where to look and what to look for.

  13. There’s a great diagram of the plug’s installation mechanism in this article. The best I’ve seen yet.

  14. Here in Switzerland, all bolts and nuts on cable cars/chairlifts seem to have torque seal on them. That could help?

    • Only if it is applied and checked. These fasteners should have had highly visible split pins securing the nuts.