From the earliest days of flight, when the Wright brothers were circling a neighbour's cornfield, birds have posed a threat to humans in the sky.
Yesterday's remarkable escape for the passengers on US Airways Flight 1549, which crashed into the Hudson River after reportedly colliding with a flock of geese, echoes an incident from Orville Wright's diary of 1905, when he reported chasing a flock of birds through the air, killing one.
Ever since, pilots and airports have worked to minimize the risk of bird strikes. More than 219 people have been killed in accidents attributed to bird strikes since 1988, and it's estimated that such collisions cause $600-million in damage to U.S. civilian and military aircraft every year.
Airports are required to have a bird-mitigation strategy and they employ flashing lights, noisemakers, guns, dogs or falcons to keep birds away from their runways.
Although bird strikes are common, they don't typically result in emergencies. Of the 1,283 bird strikes reported at Canadian airports in 2007, only three led to forced landings and 29 to aborted takeoffs.
The rest resulted in less serious effects, including 1,081 cases in which the strike had no effect and the plane was able to continue its flight.
Nick Stoss, former director of air investigations for the Transportation Safety Board of Canada, said he can't recall another incident where an aircraft of the size and sophistication of an Airbus A320 was brought down by a bird.
"In Canada we have not had that problem, where a bird strike has caused a large turbojet aircraft like the Airbus to have an accident or forced landing somewhere other than a runway," Mr. Stoss said.
"One of the parameters an aircraft engine must meet is tolerance to bird strikes. In other words, the engines are designed to withstand a certain level of bird strike, and that would be based on bird size. Beyond that weight level, the amount of damage might be significant and could result in the loss of thrust from an engine."
Captain Barry Wisnziowski, chair of the technical and safety division of the Air Canada Pilots Association, was flying an Air Canada jetliner out of Pearson International Airport last year when his aircraft struck a Canada goose. There was a bang, a thud, and then Capt. Wisnziowski decided to make a precautionary landing.
"Since you don't know what kind of damage has been caused, the prudent thing, depending on weather and environment, is to bring the aircraft back safely to the ground," he said.
In his case, the goose had hit an engine. "If you went through starlings, they would basically go right through the engine. A bird with more mass, like a goose, can do substantial damage," he said.
Airports tend to be designed to minimize pools of water or sources of food that could attract birds, but the number of bird strikes can rise during spring and fall migration. Air-traffic controllers will notify pilots if there are reports of birds in the area before takeoff or landing - the aircraft's most vulnerable points in flight.
But once a large commercial aircraft is in the air, moving at 400 kilometres an hour, it's difficult for a pilot to spot something ahead and manoeuvre out of harm's way, Mr. Stoss said.
Joe Friesen