A number found on the aircraft part washed up on the shore of Reunion, a French island in the Indian Ocean, should be the vital clue that will allow authorities to confirm quickly whether it is part of the doomed Malaysia Airlines Flight 370.

The number BB670 is visible on what appears to be a wing flap.

Former US National Transport Safety Bureau investigator Greg Feith said every manufacturer puts a data tag on every part that goes on an aircraft, apart from things such as screws.