On 22 February 1999, a Boeing 757-200 operated by Delta Air Lines, penetrated a large flock of Starlings during takeoff from Cincinnati/Northern Kentucky International Airport, Covington, Kentucky. The bird strike resulted in substantial damage to both engines but with no significant effect on the control of the airplane which made an uneventful return to land.
This is an extract from the factual Accident Report (NYC99LA064) published by the National Transportation Safety Board (NTSB), USA:
"....While taxing, he [the captain] heard no mention of a bird hazard by another aircraft or ATC. After reaching the runway, the captain initiated the takeoff with the first officer at the controls. The takeoff roll was normal until passing approximately 150 kts; at that point, a flock of birds travelling from left to right passed in front of the airplane. The captain advised the first officer of the hazard and asked him to attempt to climb over the flock. The first officer increased pitch angle, but the airplane still penetrated the flock. At the time of penetration, the nose wheel was in the air and the main landing gear was just becoming airborne. The captain advised ATC of the event, and was cleared to land.
After advising ATC, the flight crew performed [a left hand circuit to land on] runway 18L, landed, and taxied to the gate without further incident. The captain observed no change in engine performance or flight characteristics during or after the event. He added that the birds were small and brown, with white spots.
A review of the flight data record revealed that approximately 1 second after the airplane's main landing gear transitioned from ground to flight, the N1 on the left engine dropped from 81.88 percent to 56.00 percent, and the right engine dropped from 81.25 to 71.63 percent. In both cases, throttle positions remained constant. In addition, pitch was 19.16 degrees nose up, and airspeed was 152.5 knots at the time of the event.
Examination of both engines by the operator, revealed damage to the first stage of the compressor sections on the number 1, and number 2 engines....."
On February 23 and 24, 1999, a Federal Aviation Administration Wildlife Biologist examined the airport operations area (AOA). In his report, he wrote, "The starlings involved in the strike appear to have been a random foraging flock. Careful inspection of the area where the starlings were just prior to the strike did not reveal any anomalies or anything remarkably different from virtually every other grassed area within the AOA. Some winter roost can contain several million birds. Winter roosting starlings will fly up to 50 miles (one-way) daily to feed. The starlings involved in the strike could have come from the terminal roost area or they could have come from a roost many miles from the airport".
The FAA publication titled Hazardous Wildlife Attractants On Or Near Airports, states that "All species of wildlife can pose a threat to aircraft safety." In addition, it stated that starlings comprised 5 percent of all damaging animal strikes to U.S. aircraft from 1993 to 1995.
The Report does not contain any conclusion or safety recommendations.