Incident Overview
On February 24, 2005, at approximately 18:05 Japan Standard Time, a Boeing 737-400 aircraft, registration JA737D, operated by Skynet Asia Airways Co., Ltd. as Flight 119, experienced an abnormal cabin depressurization while cruising at an altitude of approximately 33,700 feet above the sea, about 170 kilometers east-northeast of Kushimoto VORTAC. The aircraft had departed Tokyo International Airport at 17:34 on a scheduled service to Miyazaki Airport, carrying 108 occupants: the pilot-in-command, four other crewmembers, and 103 passengers (including one infant).
Sequence of Events
According to digital flight data recorder (DFDR) records, ATC communications, and crew statements, the aircraft was climbing from Flight Level 310 to FL350 when, at FL337, the master caution light illuminated briefly. At 18:05:15, while at FL347, the cabin altitude warning horn activated in the cockpit. Shortly thereafter, instrument indications showed a drop in cabin pressure, leading to the automatic deployment of oxygen masks in the passenger cabin.
The crew contacted Tokyo Area Control Center at 18:05:31, requesting descent due to a problem with the cabin pressure controller. They were cleared to descend to FL260, but subsequently declared an emergency and requested 10,000 feet. Tokyo Control cleared a descent to FL150, later amended to FL140. The aircraft reached FL140 at 18:10:55. During the descent, the crew attempted to resolve the pressurization issue but were unsuccessful.
At FL140, the cabin altitude stabilized at or below 10,000 feet, and the cabin altitude warning horn stopped sounding at 18:18:45. The crew reported that the aircraft had returned to a normal state but opted to maintain FL140 as a precaution. Later, they descended to 10,000 feet after clearance from Fukuoka Area Control Center.
Crew Actions and Passenger Condition
The pilot-in-command, acting as Pilot Flying, directed the first officer to contact ATC and declare an emergency. Following the company's Rapid Depressurization checklist, an emergency descent was executed. After stabilizing at FL140, the pilot-in-command checked the cabin pressurization system and determined the cabin altitude was safe. He then contacted the senior cabin attendant, who reported that all passengers were fine, though one passenger had temporarily felt unwell.
Based on the stable cabin altitude, sufficient fuel, and recovering weather conditions at Miyazaki, the pilot-in-command decided to continue to the destination rather than divert. The aircraft landed at Miyazaki Airport at 19:15. No damage to the aircraft was reported.
Investigation
The Aircraft and Railway Accidents Investigation Commission (ARAIC) classified the event as a serious incident under Clause 10, Article 166-4 of Japan's Civil Aeronautics Regulations, citing "Abnormal Cabin Depressurization." The investigation included interviews, equipment examinations, and analysis of DFDR and ATC data. No probable cause was determined in the provided source.