On November 4, 2025, we saw a horrific accident, whereby a UPS McDonnell Douglas MD-11 crashed while taking off from Louisville (SDF), killing the three pilots onboard, plus 11 people on the ground.
Just over two weeks after the accident, the National Transportation Safety Board (NTSB) has released its preliminary report, and the findings confirm what most people had suspected.
In this post:
UPS MD-11 had fatigue cracks on engine pylon mount lug
Since there was video of the UPS MD-11 crash, we had a sense of what happened. Specifically, we know that the plane’s left engine separated from the plane during the takeoff roll, and the left wing when caught fire, putting the pilots in an impossible situation.
The NTSB’s preliminary report gives us a good sense of what happened. Of course it’s worth emphasizing that this isn’t the final report, but it definitely clears some important things up. Specifically, the NTSB found fatigue in the left pylon aft mount lug, which connects the engine to the wing.
According to the report:
After initial cleaning of the fracture surfaces, examination of the left pylon aft mount lug fractures found evidence of fatigue cracks in addition to areas of overstress failure. On the aft lug, on both the inboard and outboard fracture surfaces, a fatigue crack was observed where the aft lug bore met the aft lug forward face. For the forward lug’s inboard fracture surface, fatigue cracks were observed along the lug bore. For the forward lug’s outboard fracture surface, the fracture consisted entirely of overstress with no indications of fatigue cracking.
Now we know there were fatigue cracks, so the next big question in the investigation is what caused the fatigue cracks. All the required maintenance had been performed on the aircraft, so was the MD-11 maintenance program just not sufficient, did this plane just have too many cycles, or what?
All MD-11s in the US have been grounded following this incident, so let’s see if the planes fly again, or if something bigger is determined to be an issue. After all, these planes were presumably getting pretty close to retirement anyway.
NTSB draws parallels to 1979 crash of AA191
As many of us noted when this accident happened, this had some striking resemblances to the 1979 crash of American Airlines flight AA191, which is the deadliest air crash to ever happen in the United States. The flight was operated by McDonnell Douglas DC-10 (a prior version of the MD-11), and the plane also lost its left engine on takeoff, and immediately came crashing down.
The NTSB addresses similar events in its reports, and specifically references this accident:
On May 25, 1979, about 1504 central daylight time, American Airlines flight 191, a McDonnellDouglas DC-10-10 aircraft, crashed into an open field just short of a trailer park about 4,600 ft northwest of the departure end of runway 32R at Chicago-O’Hare International Airport, Chicago, Illinois. Flight 191 was taking off from runway 32R. The weather was clear and the visibility was 15 miles. During the takeoff rotation, the left engine and pylon assembly and about 3 ft of the leading edge of the left wing separated from the airplane and fell to the runway. Flight 191 continued to climb to about 325 ft agl and then began to roll to the left. The airplane continued to roll to the left until the wings were past the vertical position, and during the roll, the airplane’s nose pitched down below the horizon.
Flight 191 crashed into the open field and the wreckage scattered into an adjacent trailer park. The airplane was destroyed in the crash and subsequent fire. Two hundred and seventy-one persons on board Flight 191 were killed; two persons on the ground were killed, and two others were seriously injured. An old aircraft hangar, several automobiles, and a mobile home were destroyed. The NTSB investigated American Airlines flight 191 accident, see NTSB No. DCA79AA017 and aircraft accident report AAR-79-17.
Sadly, it appears that history may have repeatedly itself with this accident…
Bottom line
The NTSB has released its initial report into the recent crash of a UPS MD-11, which claimed 14 lives (three people onboard and 11 people on the ground). The NTSB found fatigue cracks in the left pylon aft mount lug, which connects the engine to the wing.
That explains how the engine separated from the plane during takeoff, causing a fire, and then putting the pilots in a situation where the plane couldn’t be saved. What a horrible tragedy, especially given the parallels to the 1979 accident of a similar aircraft. Now the question is just what caused these fatigue cracks, because that’s what regular aircraft maintenance is intended to address.
Also, massive credit to the NTSB for the speed, quality, and transparency of the investigation. We know more about this accident in two weeks than we know about the crash of Air India flight AI171 after several months.
What do you make of the NTSB’s preliminary report?
It’s worth noting that a few days ago, the FAA expanded the grounding to also include the DC-10, though there are only 8 airworthy examples registered in the US. (4 are owned by 10 Tanker Air for firefighting.)
https://avweb.com/aviation-news/dc-10-md-10-grounded-emergency-ad-md-11/
TravelinPenis...if you allowed the "orange nazi baboon" to live rent-free inside your head 24/7, then your head must been contained not more than three and a half brain cells to begin with! Give politics a rest and live a little.
Good Lord, both Tim Dunn and 1990 dispensing their turds of 'wisdom' in unison. Is there not enough suffering and mediocrity in the world??
Alter egos talking to each other (themselves).
These images are borderline nauseating. Thankful we have them, of course, to help with the investigation but it must have been a horrific task for the pilots to try and understand what was going on behind them in a critical moment of flight
That said air travel is and will remain a completely safe endeavor considering the data. I am a little worried about Boeing and Agree with comments of 'hot mess'
Typo neart the start.
McDonell should be McDonnell.
I toed a sew. I f:&;&n toed a sew.
I don’t understand why the NTSB isn’t following its usual protocols. They usually don’t dribble out information like this. The wait until they know all the facts. Speaking of facts American 191 didn’t crash because it lost its engine, it crashed because its leading edge slats, on the left side, retracted, while the right side stayed extended but the flightcrew had no indication of this because the slat asymmetry and stall warning systems did not...
I don’t understand why the NTSB isn’t following its usual protocols. They usually don’t dribble out information like this. The wait until they know all the facts. Speaking of facts American 191 didn’t crash because it lost its engine, it crashed because its leading edge slats, on the left side, retracted, while the right side stayed extended but the flightcrew had no indication of this because the slat asymmetry and stall warning systems did not illuminate in the cockpit. The left wing stalled and the aircraft went down. If the crew knew of the asymmetry they would have flown a different profile and they would have been able to fly and land the aircraft, with or without the engine attached to the wing. I don’t know why the MD11 went down but looking at the wings it looks like all of the LE devices were still extended. Let’s be patient and wait for the investigation to conclude and the NTSB issues the probable cause.
Getting a preliminary report is common within a few weeks of the accident. You also speculate yourself while asking others not to speculate. :P
What did I speculate about? Please give an example.
Don, I was just writing a response to apologize. I initially misread that you were speaking as to this flight having flap asymmetry but your entire response other than about the NTSB prelim report was about AA191. My mistake, I’m sorry! I’d edit my original comment if I could but I’m happy to own the mistake.
Not a problem. I went back and reread the -191 NTSB final report just for reference. The research and detail they went into was pretty amazing. I guess that’s why I don’t like the way they are handling this one. I’ve worked with them a few times and always found them to be very professional and somewhat reserved. I don’t know, maybe I’m just getting cranky.
What exactly is his speculation...?
@ FlyerDon -- Yeah, as noted by Timtamtrak, preliminary reports are totally standard. The NTSB is simply sharing the facts that we have as of now (fatigue cracks aren't speculation, they're a fact), though we'll have to wait for the final report to know exactly what happened.
Obviously I disagree with you. Preliminary reports are usually very basic. One or two releases and the NTSB departs the scene. It’s not like the MD11 is an ongoing problem. The planes are grounded and there is a pretty good chance they won’t be flying again anytime soon, if ever. A lot of infrequent flyers are seeing these videos, hearing about American’s accident from decades ago, and applying it to present day flying. The FAA/DOT...
Obviously I disagree with you. Preliminary reports are usually very basic. One or two releases and the NTSB departs the scene. It’s not like the MD11 is an ongoing problem. The planes are grounded and there is a pretty good chance they won’t be flying again anytime soon, if ever. A lot of infrequent flyers are seeing these videos, hearing about American’s accident from decades ago, and applying it to present day flying. The FAA/DOT are already making people nervous about flying, the NTSB doesn’t have to contribute to that. The next of kin and the employees of UPS also don’t need to keep seeing video of the accident every time they turn on the news.
@ FlyerDon -- Filing a preliminary report within 30 days is the global standard for aviation, and isn't that level of transparency good? And I'd describe this report as being pretty basic -- it just covers the basics of the wreckage found, as is standard.
And the MD-11 *is* an ongoing problem or concern. The planes are grounded pending the outcome of the investigation. If the investigation reveals there's nothing wrong with the planes, then...
@ FlyerDon -- Filing a preliminary report within 30 days is the global standard for aviation, and isn't that level of transparency good? And I'd describe this report as being pretty basic -- it just covers the basics of the wreckage found, as is standard.
And the MD-11 *is* an ongoing problem or concern. The planes are grounded pending the outcome of the investigation. If the investigation reveals there's nothing wrong with the planes, then they'll presumably be flying once again.
It seems to me that investigation transparency should be prioritized over incorrect public perception of incidents. Like, we also hear every night on the news if there's another near miss, based on ATC audio. Does that mean ATC audio shouldn't be made public?
The way news is reported has changed over time, but I don't think that's a reason to withhold information.
I agree, news gathering and reporting has changed greatly over the years but unless you work for UPS or Boeing, or you’re planning to buy an MD11, which I wouldn’t suggest doing, I think it’s prudent to let the investigators investigate and get the story off the front pages. In my view I think the lead investigator has gone way beyond a basic preliminary report and that has lead to endless speculation and I don’t...
I agree, news gathering and reporting has changed greatly over the years but unless you work for UPS or Boeing, or you’re planning to buy an MD11, which I wouldn’t suggest doing, I think it’s prudent to let the investigators investigate and get the story off the front pages. In my view I think the lead investigator has gone way beyond a basic preliminary report and that has lead to endless speculation and I don’t think that is very beneficial to anyone. When the final report comes out in the next 12-18 months I look forward to your reporting on it. And I really mean that. In the meantime, if you have time, read some of the NTSB report on AA -191. I think you will be very impressed with the effort that went into finding the root causes of that horrible accident.
Stating the parting at the rear lug had fatigue fracture as a component of the rupture is a simple factual statement. Fatigue fractures are easily and reliably identified by visual examination. There is no causation statement as to why the fatigue initiated and advanced, which would be the sort of thing to avoid this early in an investigation. All that said, I am not sure why the public needs to hear this fact about the...
Stating the parting at the rear lug had fatigue fracture as a component of the rupture is a simple factual statement. Fatigue fractures are easily and reliably identified by visual examination. There is no causation statement as to why the fatigue initiated and advanced, which would be the sort of thing to avoid this early in an investigation. All that said, I am not sure why the public needs to hear this fact about the fracture unless it is to help everyone understand this was not pilot error.
This is pretty concise and basic. In typical fashion for the NTSB, it does not jump to conclusions. However, when enough evidence can be gleaned from what they have seen so far, it's obvious that they have a pretty good idea of most of the basics and can make earlier and more directed recommendations. The MD-11F in this case has a LOT of cycles and flown hours, as expected of a freighter. Things like metal...
This is pretty concise and basic. In typical fashion for the NTSB, it does not jump to conclusions. However, when enough evidence can be gleaned from what they have seen so far, it's obvious that they have a pretty good idea of most of the basics and can make earlier and more directed recommendations. The MD-11F in this case has a LOT of cycles and flown hours, as expected of a freighter. Things like metal fatigue are well known but still not an exact science. While they are not making a final report yet until they can do their very thorough thing, I think that they have enough evidence so far that pretty much seals the MD-11F fate. Not worth it to wait 18+ months when you can draw a likely conclusion. The forces placed on the pylon at rotation are some of the most extreme it will experience, and also are at the worst possible time for fatigued metal to give way.
This does more of a service to their kin in knowing that the crew did all they could, and that future such incidents on this airframe can be prevented.
There is a lot of press pointing out this plane was old, which isn't wrong per se, but it ignores UA and DL both have multiple planes in their fleets that are all nearing the same age (75s and 76s and some older Airbuses). I get that there is some history with this general airframe of fatigue issues but it is not exactly reassuring that this was not discovered in regular maintenance and it makes...
There is a lot of press pointing out this plane was old, which isn't wrong per se, but it ignores UA and DL both have multiple planes in their fleets that are all nearing the same age (75s and 76s and some older Airbuses). I get that there is some history with this general airframe of fatigue issues but it is not exactly reassuring that this was not discovered in regular maintenance and it makes me wonder if a similar issue would be discovered for the passenger jets in general.
DL and UA don't have planes with engines falling off with the possibility that maintenance might have caused the pylon to be weakened.
Age is not the problem. taking shortcuts and doing things - whether directly through your own maintenance or through a contractor - that might be related to the most deadly aviation accident on US soil is the problem.
and, no, other airlines or their contractors don't remove widebody engines and the pylons with lift trucks.
OMG Tim "Fluffy" Dunn.
"DL and UA don't have planes with engines falling off" ?!?!?!?
CORRECTION
DL NW CO UA have ALL operated DC-10 aka. "planes with engines falling off"
Bonus for DL as they also trusted it so much they operated MD-11. The successor of "planes with engines falling off"
Yes that DL, Timmy. The successor was probably so premium only Delta Air Lines operated MD-11.
Just because engines didn't fall...
OMG Tim "Fluffy" Dunn.
"DL and UA don't have planes with engines falling off" ?!?!?!?
CORRECTION
DL NW CO UA have ALL operated DC-10 aka. "planes with engines falling off"
Bonus for DL as they also trusted it so much they operated MD-11. The successor of "planes with engines falling off"
Yes that DL, Timmy. The successor was probably so premium only Delta Air Lines operated MD-11.
Just because engines didn't fall off under their livery doesn't mean "DL and UA don't have planes with engines falling off"
eskimo,
your typically low quality posts sink to a new low.
None of DL, NW, CO or UA had engines fall off of DC10 or MD11 aircraft.
AA did and came down to unapproved maintenance procedures.
The L10 simply had far fewer engineering or operational problems; doors blew open on multiple occasions on D10s on top of the UA D10 accident caused by an engine failure taking out the entire plane's hydraulic system.
...eskimo,
your typically low quality posts sink to a new low.
None of DL, NW, CO or UA had engines fall off of DC10 or MD11 aircraft.
AA did and came down to unapproved maintenance procedures.
The L10 simply had far fewer engineering or operational problems; doors blew open on multiple occasions on D10s on top of the UA D10 accident caused by an engine failure taking out the entire plane's hydraulic system.
Eastern was also a large L10 operator; DL just outlasted EA.
given that the AA incident was caused by damage to the pylon caused by an unapproved maintenance procedure and it was still used by a UPS contractor says a significant portion of the problem was about more than just the engineering of the plane.
but feel free to tell us about the 757 and 767 engines that have fallen off in flight - on any airline for any reason.
Tim Tim Tim,
I keep forgetting reading comprehension isn't your strong point.
You can't sink lower than that.
Go read again.
And Tim, I don't know where you learn about current UPS procedures but they have banned the procedures used by AA191.
And read this again. And again. And again. Understanding anything isn't your strong point or even a skill for you.
And you probably still don't get it.
Because you're Tim Dunn.
The MD 11 sucks. They should have been grounded a long time ago with a poor track record. 757s and 767s have nothing to do with this. I was right. Well well well all you so called narcissists . The cause of the crash was due to the age of the plane.
I’m with @Jack. Before the merger, Boeing planes had comparatively few problems, after the merger where MCD management somehow came out on top the company has had one catastrophic launch after another. Coincidence?
and yet this plane was built by McDonnell Douglas. Boeing had nothing to do with it.
Yes, Boeing has had no shortage of engineering and production issues since it "acquired" McD D but this plane had nothing to do with the merger other than being supported by Boeing post merger.
There is a big difference between this accident and that of AA 46 years ago, even though the immediate cause of both accidents was the same left engine separating from the wing:
In AA's case, it was demonstrated that during maintenance, the engine was removed and placed back using a different method than that prescribed in the plane's manual. The engine separated from the pylon at the junction point because of that error.
In this...
There is a big difference between this accident and that of AA 46 years ago, even though the immediate cause of both accidents was the same left engine separating from the wing:
In AA's case, it was demonstrated that during maintenance, the engine was removed and placed back using a different method than that prescribed in the plane's manual. The engine separated from the pylon at the junction point because of that error.
In this case, the cause seems attributable to fatigue cracks. There were no such cracks on AA's DC10.
The poor engineering legacy of McDonnell Douglas lives on. It's no wonder Boeing has been such a hot mess since the merger.
Image #4 is nightmare fuel.
Those pilots are heroes to fight to the bitter end. RIP to them and the victims.
I would like to second this. Trained to do what they knew to do within all the parameters of their abilities.
May peace be with their families, their loved ones, their colleagues, and all affected during these grieving times, knowing fully Aviators love doing what they do.
The 1979 O'Hare crash occurred due to a corner-cutting maintenance practice - use a lift-truck crane to hoist the engine/pylon combo onto the wing. This is much cheaper than the recommended manner of removing the engine from the pylon. The lift truck, however, must do the practice blind to the aft point of the pylon mount, resulting in the lift track striking the metal surface and causing invisible cracks which use enlarged. The maintenance procedure...
The 1979 O'Hare crash occurred due to a corner-cutting maintenance practice - use a lift-truck crane to hoist the engine/pylon combo onto the wing. This is much cheaper than the recommended manner of removing the engine from the pylon. The lift truck, however, must do the practice blind to the aft point of the pylon mount, resulting in the lift track striking the metal surface and causing invisible cracks which use enlarged. The maintenance procedure was dropped, reportedly, but the 'stress cracks' in this left pylon appear to indicate that the same cost-saving maintenance procedure continues to be used. IPS likely will not survive this.
bold prediction.
You have to wonder why the lift truck method was not banned. and UPS undoubtedly knew what was being done.
let's see how it all falls out - this is all coming to a resolution much faster than most accidents - but the real question is why the two step engine and pylon removal process was not mandated.
The lift truck method was banned: https://drs.faa.gov/browse/excelExternalWindow/CEBF1F12352BF318862569F200688C4C.0001?modalOpened=true
“ (a) At each pylon removal and installation after the effective date of this AD, remove and install the engine and pylon separately unless removal or installation, or both, as an assembly is in accordance with a method approved by the Chief, Aircraft Engineering Division, FAA Western Region.”
Why would you assume that these stress cracks could ONLY come from that specific procedure used in 1979??
I have to say I really admire the NTSB, certainly one of the most competent federal agencies.
So, if the lug had signs of stress from age or too many cycles, why would a similar thing have happened in 1979 when the plane was much newer? And hasn't happened in the ensuing 46 years?
"I have to say I really admire the NTSB, certainly one of the most competent federal agencies."
Agreed.
Now you just have to hope that they never inspect the orange Nazi baboon's antique 757 and find anything wrong with it, because if they do, the NTSB will be dismantled faster than you can say "Goodbye East Wing of the White House."
They should rename his plane "Pedo Air."
the original investigation of the AA disaster showed that the engine had been removed from the wing using an unapproved technique which damaged the pylon.
The outcome was the same but the reasons for why it happened were considerably different.
We don't know if the cause of the latest incident could have been prevented with more intrusive inspections but the MD11/DC10 fleet left in service is fairly small - about 50 or so total...
the original investigation of the AA disaster showed that the engine had been removed from the wing using an unapproved technique which damaged the pylon.
The outcome was the same but the reasons for why it happened were considerably different.
We don't know if the cause of the latest incident could have been prevented with more intrusive inspections but the MD11/DC10 fleet left in service is fairly small - about 50 or so total in the US - and it likely will not be worth the effort to do extensive inspections or rebuilding of the pylon and its structures to keep the planes in service.
and the MD11 has been involved in a disproportionately large number of accidents related to handling - far more so than the DC10 or other models.
Thanks, that's helpful (nice to use that "helpful" button for its actual purpose!).
the 1979 incident involved the improper use of a fork lift type vehicle to change out the engine contrary to the manufacturers directives. Continental Airlines used the same procedure which caused stress and wear to the pylon. The FAA stopped that practice as soon as it was discovered.
cameras have revolutionized accident investigation esp. when accidents occur over land.
The DC-10 and MD-11 are finished.
"bold prediction."
Delta is premium.
That's a "bold prediction."
Delta flew the L1011 other than short stints of the DC10.
The L10 simply never had the operational or engineering problems the DC10 and MD11 had.
The wrong manufacturer decided to leave the commercial aircraft manufacturing business.
Delta had seventeen MD-11s