Two helicopters crashed midair in southern New Jersey in the US on Sunday (Monday AEDT), leaving one person dead and leaving another fighting for life.
The aircraft, an Enstrom F-28A and an Enstrom 280C helicopter, "collided in mid-air" about 11.25am near Hammonton Municipal Airport, the Federal Aviation Administration said.
Only the pilots were on board the helicopters when they collided, according to the statement.
Hammonton Police Chief Kevin Friel told the Associated Press responding crews extinguished flames that engulfed one of the helicopters.
The helicopters came down in a field in Hammonton and both victims were flown to the trauma centre, Hammonton Fire Department Chief Sean Macri told CNN.
The National Transportation Safety Board will lead the investigation into the crash.
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Investigators will likely first look to review any communications between the two pilots and whether they were able to see each other, said Alan Diehl, a former crash investigator for the FAA and NTSB.
"Virtually all midair collisions are a failure to what they call 'see and avoid'," Diehl said.
"Clearly they'll be looking at the out-of-cockpit views of the two aircraft and seeing if one pilot was approaching from the blind side."
Although it was mostly cloudy at the time of the crash, winds were light and visibility was good, according to the weather forecasting company AccuWeather.
Hammonton, located in Atlantic County, is about 56km from Philadelphia and sits near the New Jersey Pine Barrens, a vast area of forested wilderness.
The Hammonton Fire Department has asked bystanders to avoid the area while emergency services respond to the incident.
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