A321, en-route, north of Kaohsiung Taiwan, 2019

A321, en-route, north of Kaohsiung Taiwan, 2019


On 29 October 2019, an Airbus A321 was descending towards its destination, Kaohsiung, when the First Officer suddenly lost consciousness without warning. The Captain declared a MAYDAY and with cabin crew assistance, he was secured clear of the flight controls and given oxygen which appeared beneficial. He was then removed to the passenger cabin where a doctor recommended continuing oxygen treatment. On arrival, he had fully regained consciousness. Medical examination and tests both on arrival and subsequently were unable to identify a cause although a context of cumulative fatigue was considered likely after three consecutive nights of inadequate sleep.

Event Details
Event Type
Flight Conditions
Flight Details
Type of Flight
Public Transport (Passenger)
Intended Destination
Take-off Commenced
Flight Airborne
Flight Completed
Phase of Flight
approximately 60 NM north of Kaohsiung Airport
Inadequate Aircraft Operator Procedures
Fatigue, Flight Crew Incapacitation
Flight Crew Incapacitation
MAYDAY declaration
Damage or injury
Non-aircraft damage
Non-occupant Casualties
Off Airport Landing
Causal Factor Group(s)
Aircraft Operation
Safety Recommendation(s)
Aircraft Operation
Investigation Type


On 29 October 2019, an Airbus A321 (HL8071) being operated by Asiana Airlines on a scheduled international passenger flight from Incheon to Kaohsiung, Taiwan as AAR717 had begun descent towards destination in night VMC when the Captain asked the First Officer to obtain the destination weather via ACARS. The First Officer submitted the request but whilst waiting for the printout, suddenly lost consciousness. Cabin crew were called to assist and having briefed them on immediate actions, the Captain declared MAYDAY. The First Officer was not fit to resume his pilot role and was removed to the passenger cabin with the Captain completing the flight operating alone with an uneventful landing 20 minutes later. 


After interviewing both pilots and determining that a Serious Incident had occurred, the Taiwan Transportation Safety Board (TTSB) notified the ICAO and delegated the Investigation to the Korean Aviation Accident Investigation Board (ARAIB). Relevant data from both the aircraft FDR and CVR were downloaded and all members of the flight and cabin crew were interviewed.

It was noted that the 47 year old Captain had been employed by Asiana since 2008 and had recorded a total of 9,893 hours flying experience with the airline of which 4,026 hours were on type including time in command since his promotion to Captain in February 2018. The 27 year old First Officer had total of 836 hours flying experience which included 532 hours on type after joining the airline in April 2018 had subsequently being released for unrestricted line flying on type on 18 February 2019.

What Happened

About 30 minutes before arrival, the Captain, who was at that time acting as PM gave an approach briefing in anticipation of taking over as PF and subsequently did so. Three minutes after this, with about 20 minutes of flight time remaining, he asked the First Officer to input an ACARS request for the destination weather which he did. Then, whilst waiting for the printout, he suddenly lost consciousness. The Captain asked for and received assistance from the Cabin Crew which included immediate first aid, administering oxygen and moving the incapacitated pilot's seat back so as to prevent any interference with the flight controls. The Captain then declared a MAYDAY, advising that he intended to complete the intended flight without the assistance of a second pilot.

The SCCM subsequently stated that when first seen, the First Officer could not respond verbally but “appeared to vaguely focus when questioned”. He had been “pale, in cold sweats and his body drooped” and when the SCCM touched the First Officer’s arms “he could not sense any tension of muscle”. The SCCMs immediate ‘first aid’ response was to loosen the First Officer’s tie and belt, fit his oxygen mask and massage his limbs. After this, the pilot’s condition improved and with the abnormal pallor and cold sweats gone, some arm movement was seen and some response to questions occurred. However, despite this slight improvement, it was clear after about ten minutes that recovery was not going to be rapid enough for the First Officer to resume duty as a pilot. The Captain therefore requested that he be removed from the fight deck so having confirmed that he could move by himself, he was “guided to a passenger seat at the front of the cabin”. Once there, he was given further oxygen from a portable therapeutic oxygen bottle and more limb massage. A second call was then made to ask any passenger who was a medical professional to make themselves known to the cabin crew, an initial such call having received no response. This time, a suitably qualified passenger did respond and, after examining the First Officer, did not identify any immediate cause for concern but advised that supplementary oxygen be continued. The SCCM reported that after this “the pilot appeared to get better and showed no unusual symptoms”

A few minutes after this, the Captain completed a normal landing at Kaohsiung and on reaching the gate, a paramedic was waiting and concluded that as the patient's condition had now significantly improved, it would be fine to disembark the passengers first. Once they were all off, the paramedic was able to discuss the First Officer’s condition with him and, on checking his blood pressure, body temperature and blood sugar, found nothing abnormal. Subsequent checks were able to exclude gastroenteritis, the most frequent factor in cases of crew incapacitation. 

In a later interview with investigators, the affected pilot stated he had “felt dizziness and powerlessness, could not stay upright in the seat, recognised verbal stimuli but could not respond”. He correctly recalled most of the Captain’s actions, the sequence of cabin crew entering and their actions. A doctor from the airline's medical department saw the pilot the next day and he was given a comprehensive medical examination and then attended “consultations with neurologists and cardiologists at an external specialised medical facility over a period of a month”. After this process, the airline’s medical officer assessed the cause of the transitory incapacitation as likely (but not confirmed) to have been ‘Vasovagal Syncope’ but also mentioned that the possibility of an epilepsy origin could not be ruled out on the evidence available. In accordance with the requirements of the Aviation Medical Examiner’s Manual, the airline’s Aeromedical Examiner (AME) submitted the case for a decision by the Airman Medical Certification Board which decided that the First Officer was unfit to continue as a pilot due to being “unfit due to loss of consciousness of unknown cause”.  


  • It was noted that “In the 72 hours before the Serious Incident, the First Officer had flown about 4 hours for three days in a row from 26 April to 28 April”. Then, on the day of the event, he had arrived at the airline office at 0900 local time although the flight to Kaohsiung had not departed until over seven hours later. The First Officer stated that he had not drunk any alcohol or taken any illegal medication in the 24 hours before the flight. However, it was then found that prior to the day of the event, he had slept for only about two hours per day for three days and could be reasonably presumed to have had a high level of fatigue based on accumulated sleep debt. It was noted that the proven fact that “people are not very accurate at judging their alertness and performance after sleep has been restricted for several days” was discussed in section 2.2.1 of the current edition of  ICAO Doc 9966 where the statement “how you function versus how you feel” states as follows:

“For the first few days of severe sleep restriction (for example, 3 hours in bed), people are aware that they are getting progressively sleepier. However, after several days they no longer notice any difference in themselves, even though their alertness and performance continues to decline. In other words, as sleep restriction continues, people become increasingly unreliable at assessing their own functional status.” 

  • The Investigation reviewed the OM guidance on pilot incapacitation for both flight and cabin crew as available at the time the investigated event occurred and concluded that it had generally been followed although it was capable of enhancement. The extent to which the OM and crew training covered fatigue was also reviewed and again, whilst it was covered, it was concluded that, particularly in the context of the investigated event, the potential link between serial fatigue and the risk of in flight incapacitation was not given due prominence. 
  • The absence of an OM procedure covering controlled rest was noted as leaving no contingency option for non-augmented flight crews where one pilot exceptionally becomes aware that they may be fatigued to the extent that a proactive short period of in-seat rest may be able to resolve the problem. Appendix ‘C’ of the ICAO ‘Fatigue Management Guide for Airline Operators’ 2nd Edition 2015 was noted as the best reference for this matter

Similar Events

In the absence of any record of crew incapacitation events in South Korea, relevant evidence from elsewhere was sought. It was noted that a 2017 incapacitation of the Captain of a two pilot flight crew of a Boeing 777-200 freighter was found to have be attributable to longstanding underlying cardiovascular health issues which had gone undetected. It was also noted that a study by the Australian Transport Safety Bureau published in 2016 had found that “half of all pilot incapacitation occurrences were related to gastrointestinal illnesses such as food poisoning or gastroenteritis”. No direct reference to pilot incapacitation arising from serial fatigue was found. 

Safety Action taken by Asiana as a result of this event was noted as having included the following:

  • the simulator training scenario which covers pilot incapacitation has been changed from the takeoff phase to the descent phase where the frequency of this occurrence is higher, although this scenario does not extend the scenario until landing.  
  • newly employed First Officers  are now provided with a ‘personal life management program’. 

The Probable Cause of this Serious Incident was formally recorded as the First Officer’s loss of consciousness due to an unknown cause.

Three Contributory Factors were also identified:

  • Lack of awareness about sleep deprivation.
  • Lack of individual fatigue management. 
  • Lack of both a safety culture in the organisation and a safety mindset amongst its employees when it comes to fatigue management.

Four Safety Recommendations were made based on the findings of the Investigation as follows:

  • that Asiana Airlines emphasise each crew member's responsibility to manage fatigue and provide a means of fatigue management in detail (and provide guidance on such matters as sleep debt risk, prevention of fatigue accumulation and solutions against extreme fatigue). [AIR1906-1]
  • that Asiana Airlines incorporate ‘condition notification’ as described in the FCTM in the Flight Operations Manual (FOM) to assist in a review of the concept of ‘safety culture’ in the organisational perspective and promote it. [AIR1906-2]  
  • that Asiana Airlines should, considering the impact of enabling ‘controlled rest' on  accident prevention, set out a policy and procedure for ‘controlled rest’ (refer to the ICAO Fatigue Management Guide for Airline Operators 2nd  edition, 2015. Appendix C). [AIR1906-3]
  • that Asiana Airlines specifies the procedure for crew incapacitation in cabin crew manual and implements relevant training. [AIR1906-4]

The Final Report was published in the definitive Korean version on 14 October 2021 and in an English language version on 25 November 2021.

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