Incident Overview
During initial flap retraction after takeoff, the flight crew heard a grinding noise. Subsequently, a flight attendant reported a loud hum and vibration emanating from the right wing. The captain instructed the flight attendant to visually inspect the wing for any anomalies. The flight attendant then notified the crew of visible damage to the wing's leading edge.
Diversion and Landing
Upon learning of the wing damage, the flight crew immediately decided to divert to Seattle, Washington. The aircraft performed a normal landing without further incident.
Damage Assessment
A post-event assessment of the slat by United Airlines' engineering staff stated: "while there is no evidence of bird remains, it is our opinion that the damage was due to impact following takeoff, most likely bird, with subsequent damage caused by flight loads." The crew did not observe any birds in the area at the time of the event. The engineering staff also noted that the damage characteristics did not suggest fatigue or delamination as the cause.
Regulatory Handling
This incident was delegated to the National Transportation Safety Board (NTSB) by the Canadian Transportation Safety Board (TSB) for investigation.