Investigation Summary
Flight JS251 was en route to Beijing and had just reached its cruising altitude of 9,200 meters (FL302) near the Chinese border when the airframe began to vibrate increasingly. Passengers reported seeing a section of the wing flaps detach from the aircraft. The crew immediately initiated a turn back toward Pyongyang. This specific airframe, P-632, had been involved in another serious incident less than a year prior, involving an emergency landing in Shenyang due to smoke in the cabin. The detachment of a primary flight control surface like a flap at cruise speeds is a significant mechanical failure that can lead to loss of control, though in this instance, the aircraft remained controllable for a safe landing.
Final Conclusions
The aircraft suffered a mechanical failure resulting in the loss of a flap section. While the exact cause of the detachment (such as fatigue, corrosion, or maintenance error) was not publicly released by North Korean authorities, the event led to a safe emergency landing and the deployment of a replacement aircraft (P-633) to complete the service to Beijing.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Flaps
High-lift devices on the trailing edge of the wing; a portion of this system detached during flight.
Airframe
The structural integrity of the wing was compromised by the loss of the flap section, causing severe vibrations.
Interesting Facts
- 01The aircraft involved, P-632, was the same airframe that made an emergency landing in Shenyang on July 22, 2016, due to smoke.
- 02The vibration was reported by passengers to be severe enough to be felt throughout the entire cabin.
- 03A replacement aircraft, P-633, was used to transport the passengers to Beijing with a two-hour delay.
- 04The incident occurred just as the aircraft was about to enter Chinese airspace.
Safety Actions & Advisories
UK Travel Advice Update
Following this incident and a previous smoke-in-cabin event involving the same airframe (P-632) in 2016, the United Kingdom updated its travel advice for North Korea to include a warning regarding the safety standards of Air Koryo.
Known Controversies & Unanswered Questions
Transponder Miscoding
Reference ↗Initial tracking data suggested the aircraft involved was a Cubana Cargo Tu-204 (CU-C1703). Investigation by the Aviation Herald revealed a transponder miscode on one of Air Koryo's Tu-204/214 aircraft, which was broadcasting the ID of the stored Cuban airframe.
Location
APPROXIMATE AREA ONLY · This position predates coordinate provenance tracking. Treat it as an approximate marker for the area, not the accident site. No map is shown, because a marker here would imply a precision the record does not have.
Reported location: Near Pyongyang, North Korea