As described in 2.5.4, the PIC and the FO had conversations about feeling tired. It is probable that they were fatigued to some extent. However, the subsequent conversations in the cockpit were as usual, and their rest layover time was considered adequate according to the last 72-hour history (See Attachment 5-2). It is probable that their fatigue level was such as the crew feels during the usual international flight. Although their fatigue level at the time of the accident might not be so high as to adversely affect their maneuvering performance or judgment, it could not be conclusively determined to what extent the fatigue influenced their maneuvering performance or judgment at that time.
According to the statements of their family members and other flight personnel, it is probable that there were no problems with their physical condition and they were not fatigued. However, in case of the accident flight, the PIC and the FO engaged in two duty flight during a period of time to obtain sleep, and the accident occurred during early morning hours, i.e., the time to wake up in Asia. It is probable that the alertness and concentration of the PIC and the FO was lowered.