Everything investigators have salvaged from American Airlines crash and what it's taught us about crash with military helicopter

Investigators are working to piece together what exactly happened when an American Airlines plane and a military helicopter crashed last week (January 29), killing 67 people.

The deadliest crash in US history since 2001, American Airlines Flight 5432 and an Army Black Hawk collided midair as the plane approached to land at the Ronald Reagan Washington National Airport in Arlington County, Virginia last Wednesday.

Both plunged into the Potomac River, where recovery efforts have been taking place.

Officials confirmed today (February 5) the bodies of all 67 victims have now been retrieved, including the 60 passengers and four crew members flying on the commercial jet and the three bodies from the military helicopter. Of the 67 victims, all but one have been identified.

Wreckage from the crash is also being recovered, with hopes that data from the aircrafts' black boxes can provide crucial answers to what happened.

Here's what we know so far...

American Airlines flight recorder

The National Transportation Safety Board (NTSB) confirmed both aircrafts' black boxes had been recovered 'in good condition.'

Preliminary flight data from the American Airlines Flight 5342 presented a difference in reported altitude readings between the plane and helicopter upon collision.

Data recovered from the flight recorder inside the plane claimed it was cruising at about 325 feet, with a 25 foot margin of error on either side, according to the NTSB.

Yet, air traffic control tower data suggested that the military helicopter was flying at an altitude of about 200 feet when it collided with the commercial plane.

The approximate 100 foot discrepancy remains unaccounted for.

Helicopter black box to be examined

Emergency response units search the crash site of the American Airlines plane on the Potomac River (Win McNamee/Getty Images)

Investigators are working to extract moisture from the helicopter's black box, which was retrieved from the Potomac River on Thursday.

Officials from the NTSB confirmed the black box had been recovered and that evaluation would soon be underway.

Officials hope that flight data from the Black Hawk’s black box may provide answers to the conflicting altitude recordings.

American Airlines voice recorder

A cockpit voice recorder was also recovered from the plane wreckage and is being taken for lab analysis, the NTSB said on Friday.

Meanwhile, air traffic control audio revealed the military helicopter pilot had said he was able to 'see the passenger plane and twice requested permission to manoeuvre around it by sight and without further ground support,' Sky News reports.

Part of the wreckage is seen as rescue boats search the waters of the Potomac River (ANDREW CABALLERO-REYNOLDS/AFP via Getty Images)

So, the helicopter's pilot requested permission to proceed, taking responsibility to look out for the plane and avoid it.

The request was made in response to a question from an air traffic controller asking if he could see the passenger jet.

Jet engines

Salvage crews managed to pull one of the two jet engines from the Potomac River on Monday, along with a large piece of the plane’s exterior, officials confirmed.

A wing of the plane was also working to be recovered.

A large portion of the damaged plane fuselage lifted from the Potomac River (Chip Somodevilla/Getty Image

Preliminary report expected

Last week, the NTSB said a preliminary report about the deadly crash would be issued in 30 days.

It was been reported that only one person was managing air traffic control when the crash occurred, as per sources cited by CBS News.

Two people usually manage air traffic control for helicopters and airplanes flying in the area.

Former director of the FAA’s Office of Accident Investigation Steven Wallace told CNN he believes the cause of the disaster will present itself shortly.

“We have radar data, we have eyewitnesses, and we have all the wreckage,” he explained.

“There’s nothing missing.”