The National Transportation Safety Board released a full report of the drone incident on Thursday after first announcing that it was investigating the incident in October.

The accident occurred near Hoffman Island, NY, where drone pilot Vyacheslav Tantashov flew his DJI Phantom 4 “well beyond” his “visual line of sight,” to a distance 2.5 miles away, the report said. When interviewed by investigators, Tantashov “indicated that he was not concerned with flying beyond visual line of sight, and he expressed only a general cursory awareness of regulations and good operating practices.”

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Under current FAA rules, drone pilots are prohibited from flying drones beyond their field of vision, above 400 feet in altitude, or near restricted areas like airports. Drone operators could face financial penalties or in some cases jail time if they break the rules.

The NTSB did not say if Tantashov would face any penalties.

Tantashov also flew his drone in an area where helicopters are routinely present. At the time of the incident, the FAA had authorized the army to fly the UH-60M Black Hawk chopper in the area, and imposed a temporary drone flight restriction that Tantashov was unaware of.

Although no one was injured when the drone smashed into the helicopter, “several components” of the drone “were lodged in the helicopter,” the report said. A drone motor and a portion of a drone arm were recovered from the helicopter, in addition to debris in the helicopter’s engine oil cooler fan.

The incident comes amid concerns that an increased use of drones is a risk to conventional aircraft. The FAA released a study on drone incidents in November that said “drones that collide with large manned aircraft can cause more structural damage than birds of the same weight for a given impact speed.”