Missing flight 370 has been at the center of an enormous search since March 8, when it disappeared from radar and broke communication with the ground during a trip from Kuala Lumpur, Malaysia, to Beijing with 239 people on board. Last week, searchers were optimistic after discovering several pings that were consistent with black box signals deep in the Indian Ocean, but no new sounds have been heard since Tuesday, and now it’s feared that the batteries in the black box have died.

“We’re now into Day 37 of this tragedy,” said expert on aviation Geoffrey Thomas. “The battery life on the beacons is supposed to last 30 days. We’re hoping it might last 40 days. However, it’s been four or five days since the last strong pings. What they’re hoping for is to get one more, maybe two more pings so they can do a triangulation of the sounds and try and narrow the (search) area.”

Though the search had been narrowed down significantly due to the signals–about five were captured using high-tech listening devices–the area was still quite large, about the size of Los Angeles, and extremely deep. Searchers were given a boost of confidence after detecting the signals, but stressed to the media that there was still a lot to do.

“I’m now optimistic that we will find the aircraft, or what is left of the aircraft, in the not too distant future – but we haven’t found it yet, because this is a very challenging business,” search leader Angus Houston said. “I think that we’re looking in the right area, but I’m not prepared to say – to confirm – anything until such time as somebody lays eyes on the wreckage.”

Officials say that when they’re sure the signals are finished, they’ll send down a Bluefin 21 submersible to explore at depths of 15,000 feet, which is where the signals came from.

The Washington Post published a very informative infographic showing just how deep the plane may be here.

Australian PM 'very confident' signals are from Flight MH370's black box http://t.co/JiUEUU25v6 pic.twitter.com/raUPaDhxfb

— The Independent (@Independent) April 11, 2014

Crews are unlikely to confuse black box 'pings' with whale sounds in search for missing plane, scientists say http://t.co/Q6h610VWb6

— Mashable (@mashable) April 7, 2014

Image via Thinkstock