On May 25, 2002, approximately 1528 Taipei local time (UTC 0728),a civil transport aircraft (Boeing 747-200, flight number CI611) with 209
passengers and 16 crewmembers on board, vanished from the ATC radar
screen. The CI611 departed from Taoyuan airport en-route to Hong Kong
airport. It was later found that the aircraft had an in-flight break-up and crashed into the ocean of Taiwan Strait near Penghu Islands. The crashed site located approximately 15 NM northwest from Magong of the Penghu proper, covered an area 30 square nautical miles with an average depth of the ocean about 70 meters (230 ft). All 225 people on board Flight CI611 were perished.Aviation Safety Council (ASC), an independent government investigation agency of the R.O.C., is the investigation authority of the CI611 accident. This paper presents the ballistic trajectory analysis to assess the CI611 accident aircraft break up sequence immediately after its in-flight break-up. The results have been validated with ATC radar, Doppler weather data, and salvaged wreckage positions. The ballistic trajectory analysis confirms that the in-flight break up of CI611 aircraft initiated from the aft fuselage. Furthermore, ballistic trajectory analysis also indicated that airborne debris (papers and light materials) from the aft fuselage area,departed from the aircraft about 35,000 ft altitude, and then traveled more than 100 km to the central area of Taiwan.