New evidence retrieved from wreckage could be key to finding cause of American Airlines plane and helicopter crash

When an American Airlines passenger plane and a US Army helicopter collided in mid-air near Washington DC 67 lives were lost, 64 on the plane and three on the helicopter.

All who were involved in the crash were killed, as officials confirmed the sad news that they would not be expecting to find any survivors and were instead focused on recovering the bodies and debris.

An investigation into how this disaster could have happened is underway and one of the most important parts of the wreckage recovered are the black boxes on the American Airlines plane and the helicopter.

These are recording devices which are made to keep track of what happens to planes and the actions of the crew on board it.

The black boxes of both aircraft were recovered from the wreckage that ended up in the Potomac River by 31 January and their information is forming a crucial part of the investigation into what happened.

Black boxes from both of the aircraft have been recovered, and their data will be a major boon to investigators (Petty Officer 1st Class Brandon Giles/ U.S. Coast Guard via Getty Images)

The data collected has already found a discrepancy in the information available.

The National Transportation Safety Board (NTSB) said that the American Airlines plane was at an altitude of around 325ft at the time of the collision, plus or minus 25ft.

However, preliminary data from the air traffic control tower showed the military helicopter was recorded as being at 200ft at the same time, an explanation for this discrepancy has not yet been provided.

Investigators are hoping that by studying the helicopter's black box they will be able to explain this, though information from it is taking some time to retrieve since the device became waterlogged after the debris from the two aircraft ended up in the Potomac River.

The passenger plane's flight recorder showed a change in the pitch, but the NTSB did not say whether this was a sign that the pilots were attempting to avoid a crash with the helicopter.

The task of recovering bodies and wreckage is ongoing (Kayla Bartkowski/Getty Images)

According to Sky News, evidence from the passenger plane's black box indicated that the pilots 'had a verbal reaction' in the last moments before the crash.

Brice Banning, the investigator in charge of the case, said that 'the airplane beginning to increase its pitch' and that 'sounds of impact were audible about one second later, followed by the end of the recording'.

He said: "This is a complex investigation, there are a lot of pieces here. Our team is working hard to gather this data."

Investigators are also planning on refining the data collected from the air traffic control tower, which can be less reliable, in order to gain a clearer picture of what happened.

As of yesterday (1 February), the remains of 42 people had been recovered from the water, with 38 of those identified.