The Taiwanese Aviation Safety Council conluded their investigation into the near collision between a Boeing 757 and a Boeing 777 off Jeju Island, Korea.
They concluded that:
ICN control made a non-standard call and gave a confusing instruction to the EF306 during its descent when passing FL340. EF306 flight crew did not fully comprehend the ATC instructions, failed to confirm the instructions and stopped descending at 33,800 ft. Both parties did not apply standard radiotelephony procedures and phraseologies. These anomalies contributed to the TCAS event between EF306 and TG659. The EF306 flight crew did not complete the TCAS RA standard operation procedures and commenced an excessive high rate descent. The induced negative G-force resulted in the occupants’ injury.
There are other 8 findings related to risk which include : The EF306 flight crew did not adequately exhibit good CRM performance in this occurrence, South Sector Radar Control(SSRC) momentarily missed monitoring the approaching situations developed between EF306 and TG659 while concentrating on the radar identification of other aircraft, SSRC did not comply with ATC/TCAS operating procedures and the limited human capability during a sudden occurrence of abnormal situation who was paying attention continuously to a large number of aircraft in a relatively broad service area which was B576 that applying Reduced Vertical Separation Method(RVSM) operations. In addition, most of the injured passenger did not have their seat belts fastened and lost their protection while the fasten seat best sign was still on, the cabin crewmembers did not provide timely injury information to the flight crew, that would have allowed the flight crew to request sufficient medical assistance before landing and the controllers did not aware the importance of the number of injuries and the need for more ambulances to meet the flight upon landing. This caused the necessary number of ambulances to arrive at the airport with delay.