Navy official : ` ` We have to maintain respectful optimism and be responsible '' The Australian ship Ocean Shield picked up fresh signals that officials hope are locator beacons from the data recorders of the missing Malaysia Airlines Flight 370 . Expert says refined search is manageable for underwater vessels . Possible presence of submarine 's pingers energizes search , but for how much longer ? " : Up to 15 planes , 14 ships will take part in Wednesday 's search .
Navy official : ` ` We have to maintain respectful optimism and be responsible '' Expert says refined search is manageable for underwater vessels . Possible presence of submarine 's pingers energizes search , but for how much longer ? " : Up to 15 planes , 14 ships will take part in Wednesday 's search .