search area and still no sign of debris, it continues. planes and ships scanned more than 19,000 square miles today. the u.s. chief accident investigator says lessons are being learned in the search for the missing plane. >> water recoveries are notoriously difficult and very expensive and time consuming and so we continue to work on better recorder ta recorder technology and information coming technical briefing is being scheduled. >> we don't know at this point whether they are alive or dead. but you haven't given us any direct truth of where they actually are. we want our loved ones back. >> reporter: investigators warn this search could go on for a long time. >> at the outset, before we had