What went wrong before South Korea's deadly plane crash?

South Korea's acting president has declared seven days of national mourning to mark the country's worst aviation disaster on its soil after a plane carrying 181 people crashed on landing, killing all but two on board. It's believed the Boeing 737-800 was attempting a crash landing when it skidded off the runway, slamming into a concrete barrier. Guest: Richard De Crespigny, former Qantas pilot Producer: Linda Lopresti