Another human error may have contributed to last month’s fatal collision involving two aircraft over the Hudson River.

The National Transportation Safety Board says in radio transmissions an air traffic controller is heard giving the radio frequency for Newark Liberty airport to the pilot of the small plane involved.

When the pilot read it back, the frequency was incorrect, and officials say there was no indication that he was ever told otherwise.

The single-engine Piper plane collided with a tour helicopter on August 8, killing nine people.

Previously, federal officials had said the controller, who they say was on the phone at the time of the collision, should have warned the pilot about other aircraft in the area.

(Source: NY1)