OZ991
2011-JUL-28 · East China Sea, 130 km west of Jeju Island, South Korea

Asiana Airlines — Flight OZ991

Asiana Airlines Flight 991, a Boeing 747-400 freighter, crashed into the East China Sea after an uncontained cargo fire led to an in-flight breakup. The aircraft was carrying 58 tonnes of cargo, including lithium batteries and flammable liquids such as paint and photoresist. Approximately 50 minutes after takeoff, the crew reported a fire on the main deck and attempted to divert to Jeju Island. As the fire propagated, the crew reported a loss of flight controls and heavy vibrations before the aircraft disappeared from radar. Both crew members were killed, and the aircraft was destroyed.

Aircraft
Boeing 747-48EF
Registration
HL7604
Phase
Cause
Souls on Board
2
Fatalities
2
Origin → Dest
Seoul-Incheon International Airport (ICN) → Shanghai-Pudong International Airport (PVG)
Report

Investigation Summary

The investigation by the Aviation and Railway Accident Investigation Board (ARAIB) faced significant challenges due to the loss of flight recorders. The Cockpit Voice Recorder (CVR) was never recovered, and the Flight Data Recorder (FDR) memory module was found detached and damaged by sea conditions, rendering it useless. Investigators relied on wreckage analysis, ACARS messages, and radar data to reconstruct the event. The emergency was first declared when the aircraft was approximately 231 km (125 nm) southwest of Jeju Island, near reporting point SADLI. ACARS data indicated multiple smoke alarms in the main deck cargo area starting at 03:53 KST. Wreckage recovered from the sea floor showed evidence of intense heat and soot in the air conditioning ducts and cockpit smoke evacuation shutters. Crucially, electronic components from the cargo were found embedded in the upper wing surface, suggesting a localized explosion or high-pressure event caused by the ignition of flammable liquids. This event likely compromised the fuselage structure and flight control cables, explaining the crew's final reports of total control failure. Additionally, the ARAIB noted a safety discrepancy in training: Asiana's Boeing 747 flight simulator was configured for passenger aircraft rather than the freighter variant, which hindered the crew's ability to realistically train for main deck cargo fire emergencies.

Final Conclusions

The ARAIB concluded that a fire developed on or near pallets containing dangerous goods, though the specific ignition source could not be determined due to physical evidence destruction. The fire rapidly escalated into a large, uncontained blaze that caused portions of the fuselage to separate in midair. Contributing factors included the loading of Class 3 flammable liquids (photoresist) in position ML, and a mixture of Class 3 and Class 9 dangerous goods (paint, photoresist, corrosive liquid, and lithium-ion batteries) in position PR. The investigation also highlighted the inherent difficulty of containing a large-scale fire in a Class E cargo compartment, which lacks an active fire suppression system.

Photographic Evidence (1)

Asiana Airlines Cargo's Boeing 747 freighter (HL7604) as seen in Los Angeles, on 25 June 2011. Just over a month later, on 28 July 2011, it crashed near Jeju Island while operating a scheduled cargo service from Seoul Incheon to Shanghai Pudong.
© Rachel K. So · Wikimedia Commons

Video Analysis

No video analysis linked for this case file yet.

Airframe & Maintenance

Airframe Hours
28,752
Cycles
4,799
Engines
General Electric CF6-80C2B1F

Crew Experience

Captain

Total hours
14,123
On type
6,896

Choi Sang-gi, aged 52

First Officer

Total hours
5,211
On type
492

Lee Jeong-woong, aged 43

Systems & Failure Modes

i

Class E Cargo Compartment

A cargo compartment on freighter aircraft that relies on shutting off ventilation to starve a fire of oxygen rather than using an active fire suppression system like Halon.

i

ACARS

The Aircraft Communications Addressing and Reporting System, which transmitted critical smoke and fire warnings to the ground before the aircraft's destruction.

i

Flight Control Cables

Mechanical cables running through the fuselage that were likely severed or damaged by the intense heat and structural failure, leading to the loss of control reported by the crew.

Interesting Facts

  • 01The aircraft was carrying 58 tonnes of cargo, including 400kg of dangerous goods such as lithium batteries, paint, photoresist fluid, corrosive liquid, amino acid solution, and synthetic resin.
  • 02The fire was estimated to have caused the crash within 18 minutes of the first alarm.
  • 03Wreckage was recovered from a depth of approximately 80 to 85 meters.
  • 04The FDR was recovered in May 2012, but its memory module was missing or destroyed.
  • 05The total damage to Asiana Airlines was estimated at approximately US$190 million.

Safety Actions & Advisories

ICAO Lithium Battery Standards

Following this accident and the crash of UPS Flight 6, ICAO considered and eventually implemented stricter safety standards for the air carriage of lithium batteries.

Known Controversies & Unanswered Questions

Insurance Fraud Allegations

Reference ↗

Following the crash, rumors circulated in South Korean media suggesting the captain might have intentionally crashed the aircraft to collect on seven insurance policies totaling 3 billion won ($2.8 million). Asiana Airlines and the ARAIB strongly denied these claims, noting that the captain was a veteran pilot and that the physical evidence of an uncontained cargo fire was consistent with an accidental loss of the aircraft.

Location

East China Sea, 130 km west of Jeju Island, South Korea · 33.5333, 124.8333

Case File History

  1. CorrectionUpdated event timeline, investigation summary and open questions.
  2. Final reportUpdated final conclusions, investigation summary and findings.

Related Cases

Case ID · asiana-991-2011Last updated · Filed

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