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Investigators found fatigue cracking in a bearing assembly in the left engine pylon of UPS Flight 2976, which separated from the aircraft shortly after takeoff on November 4, 2025. A Boeing service letter dated February 7, 2011, had described four earlier failures of a similar bearing race. That history is significant, but it does not mean Boeing predicted this crash: the letter assessed that the earlier failures would not create a safety-of-flight condition, and the NTSB has not issued a final cause determination.
What failed on the UPS MD-11?
UPS Flight 2976, a Boeing (McDonnell-Douglas) MD-11F cargo flight from Louisville Muhammad Ali International Airport to Honolulu, crashed shortly after takeoff in Louisville on November 4, 2025. The left engine and its pylon separated from the wing. The NTSB’s January 14, 2026 investigative update reported that three crew members and 12 people on the ground died, including one person who died 51 days after the accident; 23 people on the ground were injured.
At the pylon’s aft mount, investigators found fractured bulkhead lugs and a spherical bearing assembly still installed on the wing clevis. The bearing race had split into forward and aft portions. Laboratory examination found fatigue cracking that began around the circumference at the edge of a recess groove on the race’s interior. The cracks extended through the race thickness and accounted for about 75% of the fracture surface; the remaining area was consistent with overstress failure. These are physical findings, not a complete explanation of how the engine and pylon separated.
Did Boeing warn airlines about this kind of bearing failure?
Yes. Boeing Service Letter MD-11-SL-54-104-A, dated February 7, 2011, notified operators of four previously reported failures of spherical bearing race part number S00399-1 on three airplanes. According to the NTSB’s account of the letter, each failure began at the interior recess groove. A fractured race could split into pieces that moved forward and aft; if displaced beyond the mount lugs, the damage could become visually identifiable.
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The NTSB said the bearing design involved in the UPS accident appeared consistent with S00399-1. The agency has not established when the accident bearing’s cracks began. The letter therefore establishes that Boeing had been told of earlier failures of a similar component design and communicated about them; it does not establish that Boeing foresaw an engine detachment or the 2025 crash.
What did Boeing’s 2011 service letter say operators should do?
| Issue | What the letter described | What the NTSB said remains under review |
|---|---|---|
| Risk assessment | Boeing assessed that this bearing failure “would not result in a safety of flight condition.” That was the letter’s assessment of the reported bearing failures, not a finding about UPS Flight 2976. | How the earlier experience relates to the accident’s full causal chain. |
| Inspection | The letter described inspecting the spherical bearing as part of the pylon aft-mount visual inspection, normally at a repetitive 60-month interval. It said the MD-11 maintenance manual had been updated to check whether the race had migrated beyond the mount-lug surfaces. | How the inspection was incorporated into Boeing and UPS maintenance documents and programs. |
| Replacement bearing | The letter described revised bearing part number S00399-523, which eliminated the recess groove, and recommended installing it when an installed bearing was found unserviceable. It did not prohibit using the older S00399-1 as a replacement. | Related Boeing–FAA correspondence and maintenance-program decisions. |
The letter’s description of an inspection and recommendation is not, by itself, proof that every operator’s federally approved maintenance schedule required the same procedure. The NTSB’s review of how the guidance entered maintenance planning and manuals was still ongoing in its January 2026 update.
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- Commemorative Collections & Gifts>- The Diecast Metal airplane model is not only a treasured work of art, but also a perfect gift for aviation enthusiasts. It allows you and your friends and family to share and reminisce the story and history of this airplane, giving you a taste of the charm and legend of MD-11 airplanes. It can also stimulate your interest and exploration of aviation knowledge and technology.
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What has the NTSB established, and what remains open?
The NTSB’s January update documented laboratory findings and a preliminary review of flight data, while stating that performance analysis and other investigative work continued. Its investigation page continued to list the case as ongoing in the materials described here. The agency had not determined when the fatigue cracks initiated, whether a particular inspection would have detected them, or the final sequence of events leading to separation.
Later proceedings added evidence and competing accounts, but did not replace a final NTSB determination:
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- Dimensions and Material: Precisely crafted 1/130 large scale airplane model for MD-11 model, Dimensions 18.70×15.79×5.31 inch / 47.50×40.10×13.50 cm. Made from high-quality resin, approximately 860g weight and excellent durability. Features hollowed-out transparent windows, realistic engine nacelles and wing for a lifelike McDonnell Douglas 11 airplane model experience.
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- May 19–20, 2026: The NTSB held a two-day investigative fact-gathering hearing. The Associated Press reported that testimony addressed a 2015 extension of inspection intervals, earlier bearing failures, and acknowledgements by Boeing and FAA officials that they had misunderstood how failure of the bearing and metal sheath could lead to broken engine-mount lugs. Hearing testimony is not itself the Board’s final finding of cause or responsibility.
- July 2026: The Associated Press reported details from a UPS docket submission about why enhanced bearing inspections had not been required in the company’s program, and the distinction between an enhanced inspection procedure in maintenance materials and requirements in the federally approved schedule. Those points are UPS’s account as reported by AP, not NTSB findings.
The final causal chain, the effectiveness of any particular inspection in this case, and the allocation of responsibility remain unresolved in the cited NTSB and news accounts.
Quick Recap
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- Dimensions and Material: Precisely crafted 1/130 large scale airplane model for MD-11 model, Dimensions 18.70×15.79×5.31 inch / 47.50×40.10×13.50 cm. Made from high-quality resin, approximately 860g weight and excellent durability. Features hollowed-out transparent windows, realistic engine nacelles and wing for a lifelike McDonnell Douglas 11 airplane model experience.
- Painted Finish: No Decals, all markings, lines, and logos are spray-painted rather than stickers, replicating the authentic airliners livery. The smooth, glossy surface exudes elegance. Regardless of the airliners paint scheme you choose, you can appreciate the exquisite details of this airplane model kit for adult, making it an ideal choice aviation collectors.
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