Search teams have begun using towed pinger locators to hunt for the black box of missing Malaysia Airlines flight MH370.
Two ships will search a 150 mile underwater path in the southern Indian Ocean.
Aviation experts say the underwater search is critical in helping to find the missing Malaysian jet.
The Australian and Royal Navy are using technology developed in the US to try to locate the 'pings' from the data recorder of Flight MH 370 which vanished a month ago.
Its a matter of days before the box stops emitting its signal
Australian aviation expert Neil Hansford explains the significance of the search.
