Part five of six. The investigation into the disaster quickly turned to the shuttle's heat resistant titles which covered the body of the vehicle. In particular, the tiles which coated the wings came under close scrutiny. Were these tiles truly as indestructible as everybody had believed? Clip taken from the BBC Horizon programme Last Flight of the Columbia Watch more high quality videos on the new BBC Worldwide YouTube channel here: http://www.youtube.com/bbcworldwide