success of flight 370 but we can be certain that we will spare no effort, that we will not rest until we have done everything we humanly can. >> reporter: the search zone remains vast, about 86,000 square miles of deep sea. >> i can promise them that we will not give up. >> reporter: in kuala lumpur, the last scheduled daily briefing is monday. it's unclear how long the search can go on without finding wreckage. but there is a deadline. the pingers on the plane's recorders are required to last 30 days, designed to last 35. key equipment to find them is arriving on board australia's ship the "ocean shield" but it won't be used until debris is found. the pinger manufacture says that it was due for an overhaul but never returned for the fix.