NEW : US Navy Response : Initial optimism over new leads becomes more cautious . Houston , a retired Australian Air chief marshal who is chief coordinator of Joint Agency Coordination Centre , warned against expecting a quick resolution . ` Search officials call new pulse signals the best indication so far they are on the right track . Without confirmation from the missing plane , nothing is certain for now . Finding an answer will take time , officials say .
NEW : US Navy Response : Initial optimism over new leads becomes more cautious . Search officials call new pulse signals the best indication so far they are on the right track . Without confirmation from the missing plane , nothing is certain for now . Finding an answer will take time , officials say .