Bart Jansen, and John Bacon

USA TODAY

The damaged cockpit voice recorder recovered Thursday from doomed EgyptAir Flight 804 could provide enough information to determine if an act of terrorism caused the crash that killed 66 people last month, a former U.S. crash investigator said.

Egypt's investigation committee said in a statement Thursday that a specially equipped ship salvaged "the part (of the recorder) that contains the memory unit, which is considered the most important part of the recording device." The Cairo-bound Airbus 320 crashed in the Mediterranean Sea on May 19, more than three hours after leaving Paris.

Al Diehl, a former investigator for the National Transportation Safety Board, said the voice recorder can provide clues on what happened to the plane and what the crew tried to do to prevent the disaster.

“It should allow them to answer most of the basic questions about whether this was a fire, explosion, mechanical issue or an act of terrorism,” Diehl said. “The voice recorder will basically take you inside the mind of pilots.”

The voices could narrate what the problem was and reveal the stress level the pilots faced. The recorder also captures all sorts of noises that can help decipher what happened to a plane. Analyzing the sounds can offer clues such as a click when an instrument is adjusted or even the sound of the engines.

The voice recorder and a separate data recorder are the black boxes — actually orange — carried in commercial aircraft. There was no immediate word on the fate of the data recorder.

The data recorder is still important to recover because it describes how the plane was functioning. Besides mechanical functions such as how the engines were running, it will include details such as whether there was a rapid decompression.

"In general terms, the data recorder tells you what happened, but the voice recorder tells you why it happened," Diehl said.

Searchers spotted the plane's wreckage Wednesday, just days before the 30-day lifespan expires on the batteries for the emergency signals emitted from the boxes. The voice recorder was being taken by ship to the Egyptian city of Alexandria, where specialists will analyze the box's contents.

The cause of the crash remains a mystery, although Egyptian officials said last week they would soon release a report on their findings thus far.

EgyptAir wreckage spotted in Mediterranean, Egypt says

The search for the plane gained traction about two weeks ago, when the French ship LaPlace detected pings from one of the plane's recorders. The Egyptian government contracted with Mauritius-based Deep Ocean Search to send the ship John Lethbridge to the scene with a remote-controlled underwater vehicle capable of scouring the sea floor nearly 2 miles deep. The Comanche 6000 vehicle uses video cameras and limbs to sample and recover objects.

On Wednesday, the Lethbridge “identified several main locations of the wreckage" and the first images of the wreckage were provided to the investigation committee. Searchers planned to map the wreckage's distribution on the seabed.

U.S. crash investigators say it can take days to produce a transcript from a voice recorder because investigators want to ensure accuracy and listen for every clue possible. Recorders are dried slowly and deliberately in a vacuum oven. The voice recorder typically captures several channels for the captain, the co-pilot and a general cockpit microphone.

The voice recorder is crucial in the EgyptAir investigation because the crew didn’t issue any distress calls before the crash. An automated system onboard the plane sent messages that smoke was detected in several locations on the jet during its final minutes.

The flight-data recorder collects more than 1,000 streams of information about how the aircraft is functioning, such as how the engines are running and alignment of wing controls.