美国有线新闻 CNN 马航MH370搜索中止 详细解读黑匣子（在线收听）

And leading things off this Wednesday, January 18th, a mystery, one of the biggest in the history of aviation may go unsolved. The underwater search for Malaysia Airlines Flight 370 has been called off. On March 8, 2014, the flight left Kuala Lumpur and headed for Beijing, China. It had 239 people onboard.

At some point during the journey, military radar indicated that the plane changed course and headed west. Investigators believe it eventually turned south, toward the southern Indian Ocean. After that, the trail went cold. A few pieces of the plane have washed up on islands near the east coast of Africa. But despite years of searching 46,000 square miles and spending millions of dollars, no one knows what happened to the plane. Its black box, its flight data recorder may hold some answers, but it's missing with the flight.

And Malaysia, China, and Australia, the three countries leading the search announced yesterday they were suspending it. They said the decision was not made lightly or without sadness.

But a group that represents family members of the flight's passengers says stopping it at this stage is nothing short of irresponsible.

RACHEL CRANE, CNN CORRESPONDENT: Following a plane crash, the search for survivors always comes first. But just as important is a search for answers, the why and the how. Often, those answers are found in a black box.

SUBTITLE: What is a black box?

CRANE: Since the '60s, all commercial airplanes have been required to have one on board. Now, the name is a little misleading because they're actually orange. And when we're talking about a black box, we're talking about two different boxes — one being the cockpit voice recorder, the other being the flight data recorder. Together, they weigh anywhere between 20 to 30 pounds, and they have to be crash-proof.

Black boxes can survive just about anything: temperatures up to 2,000 degrees Fahrenheit for an hour, forces that are 3400 Gs. Now, that's 3400 times the force of gravity. They're waterproof and they can save recorded data for two years. And it's a lot of data.

The cockpit voice recorder records that crew's conversation and background noise. By listening to the ambient sounds in the cockpit before a crash,experts can determine if the stall took place, the RPMs of the engine and the speed of which the plane was traveling. When these sounds are cross-referenced with ground control conversations, they can even help searches locate a crash site.

Then, there's the flight data recorder. It gathers 25 hours of technical data from airplane sensors, recording several thousand discreet pieces of information. Data about the airspeed, altitude, pitch, acceleration, roll, fuel, and the list goes on and on.

But to make sense of the data, first, you have to find it. Not an easy thing to do when a plane crashes into the ocean.

Both black box components are outfitted with underwater locator beacons, which self-activated the moment they come into contact with water. They sent pings once per second to signal their location and can transmit data from as deep as 20,000 feet for up to 30 days, when their batteries then run out.

But on land, there's no such pinging to help guide the search. Investigators have to sift through the wreckage until they find it.