updated 9/16/2009 4:43:45 PM ET 2009-09-16T20:43:45

The pilot of a plane involved in a mid-air collision over New York's Hudson River read back the wrong radio frequency to an air traffic controller but was not corrected by the controller, a U.S. government safety official said Wednesday.

National Transportation Safety Board Chairman Deborah Hersman told a congressional committee Wednesday that shortly after the single-engine Piper took off from Teterboro Airport in New Jersey, a Teterboro controller handed off the plane to nearby Newark Liberty International. During the handoff, the controller instructed the Piper pilot to contact Newark and gave him the radio frequency.

However, air traffic control recordings show the frequency the pilot read back was incorrect, Hersman said. There is no indication that any controller heard the incorrect readback or attempted to correct it, she said.

Crash occurred less than minute later
Less than a minute after the incorrect readback, the plane collided with an air tour helicopter, sending both aircraft hurtling into the river. All three people aboard the plane and a pilot and five Italian tourists aboard the helicopter were killed.

A preliminary review shows the pilot never contacted Newark controllers, Hersman told the House Transportation and Infrastructure Committee at a hearing on the accident.

Those controllers saw on radar that the plane was heading toward the helicopter, which was just taking off on the New York side of the river. They called the Teterboro controller and asked him to redirect the plane. The Teterboro controller twice tried unsuccessfully to contact the plane.

Hersman said investigators are reviewing recordings for other air traffic frequencies in an effort to discover whether the pilot was trying to contact Newark on the incorrect frequency.

Craig Fuller, president of the Aircraft Owners and Pilots Association, said that normally a pilot waits a moment after reading back a frequency before switching channels in case the controller wants to say something more.

"I don't know why if the frequency was read back and not understood, or if it was read back incorrectly, it was not corrected," Fuller told the committee.

Experienced pilot
The pilot, Steven Altman, 60, had obtained his license more than a decade ago and had a clean flying record that included missions taking ill patients to medical facilities.

The Federal Aviation Administration has placed the Teterboro controller and a supervisor on administrative leave pending an investigation. The controller made a personal phone call after clearing Altman for takeoff and remained on the phone chitchatting until one second before the crash. The supervisor had left the airport before the accident to run a personal errand.

Officials of the National Air Traffic Controllers Association, the union that represents air traffic controllers, said the first they heard of the incorrect readback was during Wednesday's hearing.

Ray Adams, NATCA president at Newark Liberty International Airport, said the confusion could have occurred because a controller from the Newark tower had called the Teterboro tower at the exact time the pilot was reading back the frequency. He said such simultaneous calls "have been known to happen."

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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