MH370: How can debris help air accident investigators?

A wing fragment that was found on the French Indian Ocean island of Reunion almost certainly came from missing airline MH370, according to investigators.

Richard Westcott visited The Accident Lab at Cranfield University in the UK, where air accident investigators are trained.

Prof Graham Braithwaite, an air accident investigation expert from the university, said methodical planning is needed as they often look for clues such as paint marks and tears - which could indicate what happened to the plane.