Lauda Air Flight 004

Lauda Air Flight 004 took off from Runway 21L in Don Mueang at 23:02 ICT. 5 minutes and 45 seconds into the flight, where the pilots received a "REV ISLN VAL" warning on the EICAS, to which Captain Welch replied, "that keeps coming on", indicating that the warning would come on, then extinguish. This probably made the Captain think that this warning was not true. The crew discussed the issue for approximately 5 minutes, looking through the aircraft's quick reference handbook, to which they found no action was needed, but the handbook then quoted "additional system failures may cause in-flight deployment", and to "expect normal reverser operation after landing". The captain, reassured, said that it was "just an advisory thing", and that there was "just water, or moisture in there", and moved on, the first officer shortly thereafter claiming that the captain needs "a little bit of rudder trim to the left", in response to the ailerons being slightly out of trim.

At 23:17 PM ICT (local time, 4:17Z PM), nine minutes after the first warning, while climbing past 24,500 feet, the left engine thrust reverser activated, the reverser plume causing asymmetrical lift that took away 25 percent of the original lift away from the left wing. Almost immediately, the aircraft assumed a hard left yaw, bank, and descent, with a value that peaked at -28 degrees per second. Immediately after reverser activation, the first officer noticed the discrepancy, shouting, "Shit, reverser deployed". The Captain disconnected the autopilot and inputted maximum right rudder and aileron, soon after shutting down the left engine. The airplane experienced massive negative G-forces during the descent. Contrary to existing procedures, the flight crew proceeded to pull back on their flight controls before regaining a wings level attitude. This put massive stress on the airframe as it accelerated past its maximum operating speed (Vmo), to which parts of the tail began to disintegrate. Parts of the rudder and massive areas of the right elevator began to disintegrate from the aircraft, followed by the complete separation of the right tailplane, and the breaking of the aircraft's skin.

The aircraft's tail section broke completely free of the main assembly, causing the rest of the aircraft to assume a near vertical nose down position, as the aircraft exceeded 660 knots (Mach 1). The wings then broke free of the aircraft, and the remaining fuel inside the fuel tanks ignited into a massive fireball, and the aircraft crashed into wooded terrain in the Dan Chang District of Thailand. All 223 passengers and crew died. Shortly after the accident, local villagers began to loot the crash site, uncontrolled by the local police.

Nationality	Passengers	Crew	Total
Argentina	1	0	1
Australia	1	0	1
Austria	74	9	83
Belgium	1	0	1
Bolivia	1	0	1
Brazil	1	0	1
Canada	2	0	2
China	6	0	6
Croatia	1	0	1
Denmark	1	0	1
Dominican Republic	1	0	1
France	5	0	5
Germany	4	0	4
Hong Kong	52	0	52
Hungary	2	0	2
India	8	0	8
Ireland	3	0	3
Israel	4	0	4
Italy	10	0	10
Jamaica	1	0	1
Japan	1	0	1
Mexico	7	0	7
Netherlands	3	0	3
Norway	1	0	1
New Zealand	1	0	1
Philippines	2	0	2
Poland	1	0	1
Portugal	3	0	3
Russia	1	0	1
South Africa	2	0	2
Spain	1	0	1
Sweden	2	0	2
Switzerland	7	0	7
Taiwan	3	0	3
Thailand	39	0	39
Trinidad and Tobago	1	0	1
Turkey	1	0	1
United Kingdom	2	0	2
United States	2	1	3
Yugoslavia	3	0	3
Total	213	10	223

Josef Thurner, the copilot, once flew as a co-pilot with Niki Lauda on a Lauda Boeing 767 service to Bangkok, a flight that was the subject of a Reader's Digest article in January 1990 that depicted the airline positively. Macarthur Job stated that Thurner was the better known of the crew members.[1] Thomas J. Welch, the captain, lived in Vienna,[2] but originated from Seattle, Washington.[3]

• Lauda Air Crash 1991: still too many open questions – Austrian Wings – Austrias Aviation Magazine
• "การสอบสวนอากาศยานประสบอุบัติเหต" Department of Civil Aviation (in Thai) ( Archived 2012-03-11 at the Wayback Machine)
• "Lauda Air B767 accident report" Ministry of Transport & Communications Thailand (in English)
• "Computer-Related Incidents with Commercial Aircraft The Lauda Air B767 Accident". ( Archived 2014-03-27 at the Wayback Machine) University of Bielefeld. 26 May 1991.
• Lauda Air Flight 004 (Index of articles) – South China Morning Post
• "flugzeugabsturz_20jahre.pdf" ( Archived 2011-12-23 at the Wayback Machine) University of Innsbruck. – Includes list of University of Innsbruck professors, assistants, and students who died on Flight 004
• Last flight of the Mozart (Der Todesflug der Mozart, German) – Austrian Wings – Austrias Aviation Magazine
• PlaneCrashInfo.Com – Lauda Air Flight 004
• Cockpit Voice Recorder transcript and accident summary
• Grand Prix History – Biography on Niki Lauda (Contains information about Flight 004)

1. Job, p. 204. "Of all the crew, Josef Thurner was perhaps the better known thanks to having been copilot to Niki Lauda himself on a Boeing 737 service to Bangkok which became the subject of a highly affirmative article on the airline and its history in the January 1990 issue of Reader's Digest [...]"
2. Wallace, Charles P. "'All Evidence' in Thai Air Crash Points to Bomb". Los Angeles Times. 28 May 1991. 2. Retrieved 15 February 2013.
3. "Pilots' Final Words". Associated Press]. The Seattle Times. 6 June 1991. Retrieved 15 February 2013.