previously thought. that means it used more fuel and could not travel as far. authorities indicated they have shopli shifted the search area. >> listening devices are deployed along the bottom of the sea listening for sounds from the pinger attached to the black box. they pick up a signal. it's the first sign of hope. >> we have very much narrowed down the search area. and we are very confident that the signals we are detecting are from the black box. >> but the signal fades before the black box is located. underwater vehicles that map the ocean floor are also used. 22 planes and 19 ships on the hunt. still, no answers. more than 16 months since the disappearance, authorities are still looking for the missing