All major pieces have now been recovered of the passenger plane and US army helicopter which collided in mid-air in Washington DC last week, say safety officials.
Sixty-seven people were killed in the 29 January disaster which left both aircraft in the Potomac River after they plunged into the water. The remains of all the victims have been recovered. There were no survivors.
Salvage crews have been working to recover the wreckage of the American Airlines jet and the Black Hawk helicopter.
Their black boxes have been found and crash debris is now in a hangar in Arlington, Virginia, as the probe continues.
The National Transportation Safety Board (NTSB) said: “Investigators will be looking for witness marks on the aircraft that could provide clues to the angle of collision.”
On Saturday, a plane equipped with lasers flew low over the crash scene as it scanned the bottom of the river. Crews will spend the coming days looking for smaller debris before finishing the work in around a week.
At the time of the disaster, American Airlines Flight 5342, carrying 60 passengers and four crew, was preparing to land at nearby Ronald Reagan Washington National Airport in Arlington, while the Sikorsky helicopter, with three pilots on board, was on a training exercise.
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The jet’s flight recorder showed its altitude as 325ft (99m), plus or minus 25ft (7.6m).
The helicopter was flying at 300ft (91m), which was 100ft (30.5m) over the maximum allowed for that route, the NTSB has said.
Key safety system turned off
Earlier this week, it emerged that a key safety system was turned off on the helicopter.
Senate commerce committee chairperson Ted Cruz, who has been briefed by investigators, said the Black Hawk had switched off its automatic dependent surveillance-broadcast (ADS-B), which is allowed for military aircraft.
ADS-B is an advanced surveillance technology to track aircraft location. Mr Cruz said the helicopter had a transponder so it would appear on radar but ADS-B is much more accurate.
“This was a training mission, so there was no compelling national security reason for ADS-B to be turned off,” Mr Cruz said.
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Also, the Federal Aviation Administration (has started reviewing airports with high numbers of mixed helicopter and plane traffic nearby after Mr Cruz said he had wanted a safety review.
President Donald Trump on Thursday blamed the collision on what he called an “obsolete” computer system used by US air traffic controllers and vowed to replace it.
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He has also linked a diversity drive at the FAA under previous governments to the crash.
It has since been said there is no evidence to support the president’s claim.
Last week’s crash was the deadliest US air disaster since 12 November 2001, when a jet hit a New York City neighbourhood soon after take-off, killing all 260 people on board and five on the ground.
