Why is a “black box” orange?

The search for Malaysia Flight 370 is not over yet.

The U.S. is sending special ships to locate the flight's data recorder, or "black box.”

Black boxes aren't actually black, they're orange, to make them easier to spot in wreckage. They record things like altitude, air speed and audio while a flight is in the air.

To help rescuers find them, they send out a homing signal for up to 30 days after a crash, which can be detected even when 4,000 metres underwater.

On the various challenges search crews looking for the Malaysia Airlines plane are facing, Max spoke to David Gallo.  He’s an oceanographer who helped in the search for the Titanic and co-led the search for the missing Air France Flight 447.

Gallo said the search would be getting "tougher by the day,” and highlighted some of the difficult conditions in the area – including whirlpools, bad weather, and the depth of the sea.