An investigation concluded that the aircraft, a Vickers Viscount 745D turboprop airliner, had struck at least two whistling swans, which caused severe damage to the plane, resulting in a loss of control.

The accident resulted in a greater understanding of the amount of damage that can be caused by bird strikes during flight.

[1]: p2  At 12:22 p.m., Washington Approach directed the flight to turn left to a heading of 200 degrees, which was also confirmed by the pilots.

[3][4] The impact caused the stabilizer to separate from the plane; it was found a quarter of a mile from the main wreckage.

[3] Investigators estimated that the crash might not have occurred if the two birds had hit the aircraft just a few inches higher or lower.

[2] The wreckage from the plane was spread over an area of 100 to 150 yards (90 to 140 m) in diameter, with the largest piece of debris only 15 feet (4.6 m) long.

[1]: p5  The fire removed potential evidence of additional bird strikes that may have occurred on other parts of the aircraft, but the investigators were able to recover the flight recorder.

[1]: p6  Specimens of feathers and bones found at the site were taken to the United States Fish and Wildlife Service, who identified them as belonging to whistling swans, birds that can attain weights in excess of 18 pounds (8 kg).

[4] The investigators concluded that the probable cause of the accident was "a loss of control following separation of the left horizontal stabilizer which had been weakened by a collision with a whistling swan.

The design of the Viscount 745D created new vulnerabilities because the tailplane was mounted higher than the top of the propeller discs, and therefore was unprotected.

[8] In 1968, the FAA proposed the addition of a rule requiring airplanes to be capable of safe flight and landing after an impact on the empennage by an eight-pound (four-kilogram) bird at cruising speed.