A Confusing Series of Events Following the Boeing 737-9 MAX Losing Its Plug Door

737, Alaska Airlines, Boeing

What a week it’s been in the airline industry. First there was the Japan Airlines A350 landing on a Dash-8, and now, we have the 737-9 MAX deciding to self-open a window (er, plug door) on departure. I tend not to comment on these kinds of incidents, because others have far more expertise than I. But this MAX issue… I had to chime in since the reaction/response has been so frustrating all around.

On Friday evening, Alaska flight 1282 departed Portland (OR) for Ontario (CA). The flight was operated by N704AL, a nearly-brand new Boeing 737-9 MAX. The airplane first entered revenue service for Alaska less than two months earlier on November 11. As the airplane climbed out of Portland, a door on the left-hand side ripped away from the fuselage and disappeared into the night. Nobody was hurt, but there were reports of a guy sitting in that row who had his shirt sucked off his body, which I guess we’ll assume was related to the incident and not another case of “customers behaving inappropriately.”

This newfound gaping hole obviously caused an explosive decompression, so the oxygen masks dropped. The pilots turned around and landed back in Portland, as uneventfully as possible considering the situation. There were some minor injuries, mostly to the young men and women who fainted from being overwhelmed after seeing that guy without a shirt on.

But let’s talk about this door, because it’s not just any door. Boeing built the -9 with a door back between the wing and the tail. You can see it vaguely in this photo if you look where there appears to be a gap between the windows.

Photo via Boeing

Only airlines with very dense configurations activate that door, because they need more ways to evacuate all those people in order to pass the regulatory time requirements. I know flyDubai does and a couple other small airlines, but most do not need it. That’s the case for Alaska, United, Copa, and Aeromexico, the largest operators of the aircraft.

When you look at the outside of an Alaska Airlines airplanes, you can see where the door is.

Image via Alaska Airlines

But on the inside, you would have no idea that there even could be a door there. It is plugged — technically a “plug door” — and the interior sidewall goes right over it so nobody would even realize it was there. That’s why it doesn’t even show up on the seat map.

Image via Alaska Airlines

To be very clear, this does not exist on the shorter 737-8 MAX. That giant sigh of relief you heard was from Southwest which operates more than 200 of those airplanes. But the same thing does appear on the 737-900ER from the previous generation of 737, so this setup has been flying for years.

With this specific airplane being almost brand new and the problem happening to a plug door that regular people and even most employees wouldn’t access, it seems likely that this is a manufacturing issue. Or not. Maybe it’s an installation issue. Or maybe it’s a completely random fluke. We just don’t know for sure, and that’s why what has happened since the incident is so puzzling.

Alaska was quick to say it was grounding its fleet until inspections could be completed, but then almost immediately there were -9s in the air flying revenue flights. It was later clarified that some of the airplanes (18 at Alaska) had just been through maintenance checks that included inspections in these areas, but that couldn’t have instilled confidence in those about to board the airplane while watching what had just happened on their phones or televisions.

A day later, the Federal Aviation Administration (FAA) chimed in with an emergency airworthiness directive. Those airlines that have the airplane with the plug door had to inspect their aircraft before flying them again… if they hadn’t recently had a heavy maintenance check which, as mentioned, did the same work. Or maybe not. By the end of Saturday, all of the -9s were grounded, even those that had been previously cleared, until an inspection.

According to Alaska, this was going to be the case until “details about possible additional maintenance work are confirmed with the FAA.” Disruptions could extend through mid-week, according to the airline, though I’d put my money on it dragging longer than that. United has put out statements as well, saying that it has 79 of the aircraft, none of which are flying now, while providing detailed information about what is going on with its operation. More recent statements from the airline basically say “we’re waiting for the FAA and Boeing to tell us what the hell is going on.” 

Boeing has been mostly silent throughout this whole thing, at least in the public sphere, which must be driving all airlines insane even though it’s entirely on-brand. Boeing’s two statements (one, two) said absolutely nothing except that they admit they know something happened. The burden has fallen on Alaska and other airlines to put out information. They have been pumping out details when they can, but why is the message so confusing? 

The planes are grounded… but they aren’t all grounded… but yes they are. Maybe this is because Boeing and the FAA can’t make up their minds and Alaska is just following them. Or maybe the airlines just aren’t being conservative enough. I’m surprised they didn’t just ground the airplanes until they knew more.

By Sunday morning, the FAA put out a tweet which I honestly can’t believe had to be put out there.

We’ve received a lot of questions about what the Emergency Airworthiness Directive means.

The FAA’s first priority is keeping the flying public safe. We have grounded the affected airplanes, and they will remain grounded until the FAA is satisfied that they are safe.

What on earth does that even mean? Just a day earlier the airplanes were still flying around freely after some were grounded. The FAA presumably changed what it wanted inspected. Now we’re all supposed to just trust that when the FAA thinks it’s safe, then it’s safe, though there’s no information beyond that. The FAA should act quickly, be clear and decisive, and always err on the side of safety. That is not how the FAA came across this weekend.

Clearly there’s been a concern that there could eventually be some issue with the plug door. That’s why there was an inspection process in place to ensure that everything was ok during regular maintenance checks. But that is clearly not enough since we don’t know what actually happened here. They didn’t even find the plug door until late Sunday night. What failed? Why is the -900ER not impacted even though it has the same setup? Is something different? What do they know? Boeing and the FAA have been silent on this, and the silence is deafening.

The airplanes should have been grounded right away until there was enough information, and all this flip-flopping on inspections should never have happened. This is not how parts of brand new airplanes are supposed to work, and until they know what happened, the airplane should not be carrying passengers. Everything we saw over the weekend felt like safety theater.

The thing is, it’s not like this was a structural failure. It shouldn’t be all that hard to find what happened and fix it, once they find the plug door itself (or they’ve had more time to do testing on the frame). Until then, there is a risk that if it happens again, someone could be sitting in that window seat and might leave the airplane involuntarily. Or it could happen at altitude where people might be unbelted. Even if the airplane is flyable, fatalities are entireily possible. Better safe than sorry right now; keep the airplanes on the ground.

In the meantime, since Boeing and the FAA aren’t saying anything useful, I’ll stay glued to The Air Current like the rest of you — its safety coverage is made available without a subscription, but you should still subscribe — waiting to see what the heck actually happened here.

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73 comments on “A Confusing Series of Events Following the Boeing 737-9 MAX Losing Its Plug Door

  1. Wow, Brett… Just when you thought you had Monday’s post written & updated on the JAL A350 incident, you had to pivot to focus on the 737 Max door plug. Keeping you on your toes!

    I also hope to see your take/analysis of the airlines’ response to the big storm that hit New England over the weekend as well (especially as another storm is on the way) as well, even if it’s just “snow sucks unless you’re skiing in it or looking at it through a window, airlines did reasonably well with their IRROPS procedures”.

    Regarding doors, I think the real solution is to just hermetically seal pax in planes made a single drawn piece of material without any doors (“time capsule style”), so that there are no doors or door plugs to fail or worry about. Surely THAT would solve the problem! /sarcasm

  2. The 900ER hasn’t ever had an issue with its plug doors, yes? Or no? Maybe that’s why they weren’t affected?

    1. NSS – Not that I know of, but we don’t know what happened here so in theory it could impact those airplanes if they have the exact same construction.
      Maybe not, but this information vacuum leaves a lot of questions up in the air.

    2. And Alaska’s oldest 900 is 23 years old.

      another interesting tidbit – this airframe in particular was one delayed due to the strike by Spirit Aerosystems, the company that Boeing outsources to actually *make* the plane.

      (not sure if people realize Boeing really doesn’t do AS MUCH as they used to…. its a puzzle maker putting the pieces together)

      1. Fun Fact too – Spirit Aerosystems used to be part of Boeing. Until Boeing realized they could spin off the company, make a bunch of money in the short term, and then buy fuselages back from them. Talk about penny-wise but pound-foolish…

        1. It is common to use suppliers in aircraft manufacturing. Most components on a plane are outsourced (avionics, landing gear, power plant, seating…) Boeing and Airbus are essentially assemblers of outsourced components.

      2. Those 23-year old Alaska -900s are not part of the equation because they don’t have the plug.

        There’s a distinction between a Boeing 737-900 and a -900ER. The -900s were released first, do not have provision for an emergency door (or plug) and have the same hard 189 seat exit limit as a -800. In other words, they are just a stretched -800.

        The 737-900ER came later and has either an emergency door or plug, depending on the airline. I think they also have a revised rear bulkhead, plus I think they have longer range (hence “ER”).

        I think the oldest AS 737-900ERs are about a decade old.

        The 737 MAX 9 is based on the 900ER, not the 900.

        1. The -900ER has a rear flat bulkhead (instead of the typical pressure dome bulkhead). The flat bulkhead allows a couple more rows of seats and hence the added mid exit doors, but as mentioned most -900ER and MAX-9 usually have door plugs because they don’t exceed the 189 pax threshold

  3. My gosh, the 737 Max is becoming the DC-10 of the new millennium. The plane is snake bit, to put it mildly.

    It would appear the NTSB and FAA both are doing what they’re supposed to do: gather information, order inspections and urge caution. But when the political class starts speaking, both agencies have to show they can be the toughest regulatory hombre on the block. Hence, the panic, groundings and wailing about “what went wrong.”

    One disconcerting problem in aviation is the continued quality control problems at Boeing. These are unbecoming a world-class plane maker. Maybe they’re happening at Airbus as well and, for whatever reason, we don’t hear about it. I’m candidly guessing quality control issues don’t occur at Airbus at anywhere near the level we’ve seen at Boeing recently.

  4. Appreciate this post. I thought AS knew what was the root-cause – hence quickly ‘checked’ 18 of them within hours of the incident and flew them again. This shows that AS’s safety bar is as low as Boeing’s. UA is not far behind – initially grounded only those delivered around the same time with the troubled fleet (probably makes sense at that stage) before FAA ordered to ground’em all.

    1. Frontier, Spirit, and jetBlue are the most safest airlines in the US because they are all Airbus

      1. Tell that to the families of AF447 which took 228 lives. Last fatal US commercial crash was 2009. All US airlines are safe.

    2. hk – I don’t understand how Alaska could know the root cause that quickly.
      Feel free to link if you saw that info somewhere. They may have their suspicions, but I don’t know how they would know what really happened.

  5. I like your photo and commentary in the 1st photo. This reminds me of when AA took “DC-10 Luxury Liner” decal off the front of the DC-10.

  6. Correct me if I’m wrong, but I thought I remembered reading that opening doors or windows while pressurized was theoretically impossible because they open inwards first, before pivoting outwards (in the case of a door). Is that different in the case of a “plug” where it can just blow outwards? That seems…not ideal.

    1. That’s correct. The name itself says that – “plug”. When a door is secured, it’s literally plugged into the fuselage from the inside, the pressure differential holds it in place even more tightly, like a plug in a sink.

      Key info is whether -9 and -900ER design for the plug door changed. And then you can’t help wondering if perhaps the reason this point has not been emphasized is bc no one wants the -900ER grounded as well.

      If someone put a gun to my head, I’d say manufacturing defect. That would be a best case news for AS and Boeing at this point. If it turns out it’s a design defect, that’s going to cost a lot of people a lot of money.

      It’s disturbing that apparently this aircraft had repeated pressurization warnings but was permitted to keep flying.

      1. Judging by the limited photos available, it appears the plug is mounted from the outside and secured by bolts that are secured by a series of mounts located around the fuselage frame. If the bolts came loose, it stands to reason that the cabin pressure pushed the plug outward.

        1. I’m no physicist or aerospace engineer but why not mount the plug from the INSIDE then?

  7. Also, it seems the depressurization blew the cockpit door open. That also seems like a new threat vector worthy of consideration.

    1. That is shocking considering we’ve been told how well the cockpit door is secured post 9/11. I guess we shouldn’t be shocked by anything anymore but this is a huge problem and seems like it should require inspection and or corrective action as well.

    2. The cockpit doors have “blowout panels” to equalize pressure for just this situation. It wouldn’t be the entire door. I’ll double check at work but pretty sure the design hasn’t changed since the armored door changes post 9/11.

      1. It might be that the MAX design is different. I’m back to work Thursday and will seek out a -900 and take a look. We don’t have MAX’s luckily…

  8. I’m a little confused why the -900 and -900ERs with plug doors are still flying, since my understanding is that nothing changed in the plug door design between the two generations. Do they know that it’s a MAX-specific issue? I mean it *could* be related to some change in manufacturing processes, and the fact that this happened to a brand new plane after not happening in probably hundreds of thousands of -900 flights is certainly suspicious, but given that they have no idea what the cause is, allowing -900s to continue flying seems like erring on the side of operational expediency rather than safety.

    1. Alex – Yeah, we don’t know. Maybe they know something that they aren’t saying. Since it’s such a new airplane, it certainly points toward either a manufacturing or install defect. So maybe they already know something that suggests that the old -900s don’t fall into that batch of incompetence. But I find the silence awfully strange.

    2. At this point, all 900ERs have been through a HMV (or 2 or 3) in which the plug is inspected and bolts checked. A 2-month-old plane would not. This at least suggests a manufacturing issue rather than a broader design flaw. But I agree with Cranky that the lack of clarity from the regulator is not helping.

  9. There are hundreds of planes with similar plugs, and none of them have had issues, so it’s not the plug itself, so most likely it’s some issue with this plane.

    Quick note: the FAA grounded American companies from flying it, but several countries are still allowing airlines to fly them, including Panama and Iceland.

    The FAA did NOT ban the Max 9 from US airspace, as both COPA and Icelandic have Max 9 flights to or from the US in the air right as I type this.

    1. I believe COPA and Icelandair Max 9s are the ones that actually use the emergency exit rather than having the plug. I assume that’s why they’re still flying around.

  10. When you see the words “we take safety seriously or safety is our highest priority,” you know it’s all theatre as every press release has those same buzzwords laced throughout.

  11. Excellent writeup on an event from which we still have very little information.

    Also interesting to see reports that the cockpit voice recorder was completely overwritten. I would have assumed there is a procedure in place to prevent this in the event of an accident.

  12. The shutdown of the 757 production line just keeps showing us how dumb Boeing is, year after year. I bet they wished they had quit the 737 after the NG and moved forward with the 757 and additional variants.

    1. I think this exact same thing every time I get on one of these ridiculous frankenjets. Decades of tarting up this 1968 Pinto when they should have instead updated their 1982 Cadillac. All because of Southwest, Ryanair and the influx of McDonnell Douglas penny pincher types that destroyed Boeing’s culture of innovation and excellence.

      I’ve tried to stay supportive but the sad fact is that Boeing just doesn’t appear to be very good at making planes anymore.

      Or designing them. Their last clean sheet design was over 12 years ago with the 787 in 2011, 4 years late due to myriad problems and still plagued with manufacturing issues to this day.

      Compare that to this run of new product launches: 727 (1964), 737 (1968), 747 (1970), 757/767 (1982), 777 (1995), 787 (2011). Coming soon – nothing! There is no clean sheet product in design now or even contemplated. It will likely be 25 years or more between new product launches. Sad commentary on a formerly great company.

      1. How could I omit the 707, first flying in 1958? If you really want to make your head hurt, your apple watch probably contains more computing power than existed in all of Boeing’s mainframes during the design of many of those planes. Not to mention not having any PCs, CAD software, etc.

        If there are any latter day Kelly Johnsons (yes I know that was Lockheed but give be a little latitude), they are suffocated and marginalized in pursuit of inflating the bottom line, the only real innovation occurring in this industry anymore.

    2. The 757 shouldn’t have been discontinued but I can see why the 737 was prioritized instead, it’s much more versatile and popular. After the NG, Boeing should’ve done a full clean slate redesign of the 737, but faced heavy pressure from Airbus who was quickly developing the NEO, as well as airlines like Southwest that complained about not wanting to retrain pilots on a new aircraft type. I can’t blame Boeing for feel pressured into creating the MAX instead of a clean slate design, but the oversight in safety is obviously problematic.

        1. Agreed, using the standard of both…75-2 and a 73-8. The 75 can carry just shy of 30 more passengers, 1/3rd more cargo and still land and take off in a shorter distance. The 75 doesn’t also narrow in at the front making first class less classy. The only thing the 73 has going for it is you don’t need airstairs or ramps to access it. So I guess versatile for the “backcountry” if your backcountry has a long enough field.

          1. Actually that “feature” is what directly caused the two MAX crashes. The 737 airframe is so low to the ground (in order to accommodate the long ago useless belly stairs), that, as the airframe was stretched beyond common sense and engine sizes increased, the plane’s center of gravity is completely out of whack (technical term).

            In order to keep updating this inferior, outdated airframe, they had to develop the now infamous MCAS software known to push the nose down so they could continue to violate basic rules of physics. How did that work out again?

            The 757 airframe, in addition to all the things you mentioned, also has much greater range, MTOW, high altitude and short runway performance, etc. And, success the fuselage is far enough off the ground, MCAS would have never existed.

            1. Keep in mind that Boeing designed the 367-80, KC-135 and 707 to be low to the ground so that the engines could be serviced without a platform, so low in fact that the main gear required bi-fold doors. Douglas obviously didn’t have the same philosophy and as a result, it was easier to re-engine the DC-8 in the 1980’s. As far as the 757 is concerned, isn’t the cross-section the same as the 727, coming off the same assembly line?

            2. Hey Marc, this article does a much better job of making my argument. But the short story is this:

              The bottom of the 737’s engines are a minimum of 17 inches above the runway. By comparison, the Boeing 757 has a minimum clearance of 29 inches, according to Boeing specification books. The newer 787 Dreamliner has 28 inches or 29 inches, depending on the engine.


  13. It may be time for Boeing to rebrand the “max” name and drop the moniker. McDonnell Douglas did just that with the DC-10, eventually rebranding the product line “MD”.

    1. FedEx drove the DC-10 to MD-10 rebranding. The DC is a three pilot cockpit. The MD is a two pilot cockpit. No MD-10s were delivered by McDonnell Douglas. They were all converted from DC-10s.

        1. DC = Douglas Aircraft Company aka anything in development prior to 1967
          MD = McDonnell Douglas aka anything developed between 1967 and 1997.

            1. It was already in development before the merger so I guess it wasn’t renamed.

            2. As I understand it, the DC-10 was developed by Douglas before the merger.
              It came out of a previous military design that wasn’t taken up. When the merger happened in April 1967, it hadn’t been greenlit yet, I don’t think.
              But they were already well down the path with production beginning in 1968. So while McDonnell did actually make this come to fruition, there was no new commercial aircraft that was ever truly designed and built by McDonnell Douglas. Everything after that was a derivative. If anyone knows more about the timeline, I’d be curious to hear if I was wrong on that.

      1. There weren’t any MD-10s, only MD-11s. But yes the MD-11 was basically just the next generation of DC-10, just like MD-80s were next gen DC-9s. And the laughable 717 designation which Boeing slapped on the MD-95 after buying McDonnell Douglas.

        1. Oops, correcting myself. Today I learned that there were MD-10s which, as Nick correctly pointed out, were essentially DC-10s with glass, 2 pilot cockpits. Sorry Nick!

    2. I think it had more to do with Douglas (DC) merging with McDonnell and forming McDonnell Douglas (MD).

  14. Literally right below the headline of the AS 737 Max incident on Apple News is a related story on Boeing asking the FAA for a waiver on the 737 Max 7. You can’t make this stuff up…timing and all.

    1. As Angry Bob put it above… And Boeing has the gall to ask the FAA for a waiver on their 737 Max 7.

      Couldn’t agree more.

  15. I was supposed to fly on AS740 (SFO-LAS) on Saturday at 9:35pm. I woke up Saturday morning and saw the news about the incident from the night before and checked on my flight and sure enough, MAX-9. Our tail only had one scheduled flight before ours and it had been canceled, so I kept waiting and waiting to see a cancellation or a tail swap, but I didn’t hear anything all day. I thought maybe our tail had been one of the “25%” that had been inspected and released.

    Sure enough, just as I was starting to think about leaving for the airport around 6pm, I got the cancellation notice. Half an hour later, I got an email from Alaska saying I had been rebooked on a flight for the next morning….to Seattle. Oops.

  16. CF – many thanks for chiming in on a very topical news item! Some of the commentary is also very interesting..than you, one and all!

  17. I’m flying later this week on a delta 900ER, then back on Alaska. And yes the silence is deafening.

    How are we supposed to trust the 900ER is safe when they haven’t isolated the root cause of the Max 9 issue and we know Boeing’s quality has been crap for at least 10 years?

    And how the heck is AS going to be flying anything close to their full schedule with 1/3 of their mainline fleet out of commission.

    So frustrating.

    1. Previous 737s didn’t have build problems. This isn’t about design. When multiple recent aircraft have similar problems that didn’t exist before something changed. The NTSB will figure it out

  18. Let’s not forget that at the end of 2023, the FAA advised ALL operators of the MAX to check the rudder control systems for loose bolts after finding 2 aircraft with issues, one with a missing bolt and a pre-delivery aircraft with a bolt not tightened to spec.


    There seems to be a culture issue at Boeing. They need to stop trying to be the “darlings of Wall Street” and get back to building the best and safest aircraft the world has ever seen. QA/QC at Boeing needs to be invested in. MAX, 787 issues, KC-46 issues, etc..

  19. Starting to think Boeing needs a mass clearing out in both corporate culture and manufacturing. Their two most recent projects (787 and the MAX) have had repeated issues although the 87 has turned out to be a good plane. They had issues on the military side with the Stratotanker project. And of course, lest anyone forget, they failed to think about and develop a successor to the 717 and had to use their lobbying prowess to basically screw over Bombardier and deliver the C-series to Airbus for what ended up being a $5 billion loss to the government of Canada and Bombardier while getting no further revenue from the program.

    I’m thinking the 900ER is going to be OK. It’s been around a while without any issues.

    1. They’ll just move the corporate headquarters further away from Seattle, their engineering and manufacturing center, again. Oh wait, they’ve already done that. As if Chicago wasn’t far enough, they are now moving one time zone further, decamping here in (or near) our Nation’s Capitol.

      Proving the point that government contracts are what drives this company now, certainly not innovation and not even commercial aviation anymore.

      1. It was bound to happen, that the company would be run by shrewd Wall Street types whose only interest is in shareholder value. Why wasn’t this an issue when William Allen and Malcolm Stamper ran the show so successfully?

  20. Well the good news is that Boeing and their sub-contractor both going to “get better”. Don’t you feel better now?

    “We’re going to get better,” a Boeing news release says Calhoun told employees. “Not because the two of us are talking, but because the engineers at Boeing, the mechanics at Boeing, the inspectors at Boeing, the engineers at Spirit, the mechanics at Spirit, the inspectors at Spirit. They’re going to speak the same language on this in every way, shape or form.”


  21. For all of you talking about extending the Boeing 757 model, my observation is that 757s only ever see to have been popular in the US. 737s are popular worldwide.

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