It has now been five days since the last ping, possibly from Malaysia Airlines Flight 370, was heard.
Crews expanded the search area Sunday, looking for any possible signs of the missing flight. Searchers believe the four pings they heard last week likely came from the so-called black boxes, but they need to find solid evidence.
“They’re being very cautious. They don’t want to come out and say this is definitely the black box until they have a photograph of wreckage at the bottom of the ocean,” said Tom Ballantyne, chief correspondent of Orient Aviation. “That’s what they want. They want eyes on before they make a definite statement."
Time is of the essence as the search for Flight 370 has taken longer than 30 days -- the life expectancy of the batteries used to send out signals from the black boxes.
“More than likely, they are reaching end of life or already have. We’re at Day 37. … If (a beacon) is still going, it is very, very quiet at this point,” Jeff Densmore, director of engineering for Dukane Seacom, told CNN’s Candy Crowley.
Flight 370 vanished March 8 with 239 people aboard en route from Kuala Lumpur to Beijing. Officials said, based on data analysis, the flight “ended" in the Indian Ocean.
CNN Wires contributed to this report.