At 01:52 am local time on 21 December 2002, the ATR 72 operating the flight crashed into the sea 17 kilometres (11 mi; 9.2 nmi) southwest of Magong, Penghu, Taiwan.

At 08:05 one of the rescue boats found the first pieces of debris and subsequently confirmed that Flight 791 had crashed.

[5][6] From September 1998 to February 2001, the aircraft was leased to Gill Airways in the United Kingdom with British registration G-BXYV.

After returning to TransAsia Airways in 2001, the aircraft was converted into a freighter and was given its previous registration back as B-22708.

First Officer Liu Ching-hai, aged 34, had been with TransAsia Airways since 1997 and had logged 4,578 flight hours, with 4,271 of them on the ATR 42/72.

[1]: 5–6 The majority of the wreckage was found 180 metres (590 ft) away from where Flight 791 last made contact with ATC.

[1]: 107  On 9 January 2003, the ASC commenced a salvage operation assisted by the coast guard administration and TransAsia Airways staff.

A short non-pertinent conversation was then heard, after which several alarms sounded until the end of the recording.

After the first officer requested and obtained clearance to descend by ATC, the captain again said that there was ice accumulating on the aircraft.

The attempt was unsuccessful and the aircraft rapidly lost altitude and crashed into the Ocean, killing the crew.

The report determined that the flight crew had lacked situational awareness and thus did not respond to the severe icing conditions.