Sonic Search Zone News Today

As i just mentioned, in fact, its been four days now since they recorded and detected any pings from the emergency beacons on those black box flight recorders. so i think theres a sense in which, you know, hope is diminishi diminishi diminishing somewhat, fredricka. >> what about the planes up in the air? how are they assists in the search? >> reporter: its a kind of separate search, although there are some planes involved in the acoustic search as well dropping sonar buoys into the water to try...