signal. but as our aviation correspondent explains, that transponder will soon run out of power. >> reporter: this debris may be the best hint yet to what happened to flight 370. but even if it is from the missing plane, the real key to understanding what happened could be miles away at the bottom of the ocean and it's calling but time is running out. the cockpit voice recorders stores at least two hours of data and the recorder stores 36 hours of instrument data. both crucial to what happened. transmitters send out a locating tone but that only lasts for 30 days. malaysian officials say without the pings, they don't have the technology to find them on their own. >> before that becomes an issue, let me tell you that the malaysian submarines do not have