Aircraft collisions with birds and other wildlife are more than a serious safety threat to airlines, the economic impact of wildlife strikes against aircraft is estimated to be $600 million in damage to aircraft in the U.S. every year, according to the Bird Strike Committee USA.

Indeed, the U.S. Department of Agriculture (USDA) estimates that wildlife strikes cause more than 550,000 hours of aircraft downtime and cost U.S. civil aviation in excess of $500 million every year. As noted by the FAA in 2004, wildlife strikes worldwide cost civil aviation an estimated $1.2 billion annually a safety and economic concern for the U.S. aviation industry because of expanding populations of many wildlife species that are hazardous to aircraft.

Military aircraft are also not immune from avian threats. Last year alone, the U.S. Air Force experienced more than 4,000 bird strikes, said Eugene LeBoeuf, chief of the Air Force's Bird/Wildlife Aircraft Strike Hazard (BASH) program at Kirtland AFB, NM. While none of those bird strikes was classified as a "Class A" accident, one that results in a death or more than $1 million in damages, LeBoeuf said, but collectively they cost the U.S. taxpayer an estimated $35 million.

The Federal Aviation Administration (FAA) has collected reports of wildlife strikes to civil aircraft in a national database since 1990. Twenty-four of the 36 largest bird species in North America have shown significant population increases in the past 30 years and only three species have shown declines. The non-migratory population of Canada geese more than tripled from 1.0 million to 3.5 million birds in the United States.

To make matters worse, modern turbofan-powered aircraft, with quieter engines, are less obvious to birds compared to noisier piston-powered aircraft and older turbine-powered aircraft.

The FAA database (1990-2006) contains about 73,500 reported strikes, about one strike for every 10,000 non-military flights. About 85 percent of these involved commercial aircraft with the remainder spread among business, private, and government aircraft. About 7,100 wildlife strikes were reported in 2006 compared to 1,700 in 1990. In 2007, over 7,600 birds and other wildlife were reported to have hit civil aircraft in the U.S. This number equates to 1.751 bird strikes per 10,000 aircraft movements.

USDA data shows that approximately 97 percent of wildlife strikes are bird strikes. Most bird strikes (62 percent) occur during the day and most (60 percent) occur during the landing approach, or landing roll phase of flight and fairly close to the ground. Sixty percent of bird strikes occurred at 100 feet or less AGL, 73 percent at 500ft AGL and 92 percent at 3,000 feet or less AGL.

Peggy Gilligan, the FAA’s associate administrator for aviation safety, recently said that “our statistics on bird strikes indicate that the closer the aircraft is to the runway, the higher the risk of a bird strike. Conversely, the risk of a substantial bird strike decreases significantly with altitude. High altitude strikes are not common, though they do occur. For instance, at 30,000 feet, there was only one reported bird strike, between 1990-2008.”

As the ditching of US Airways Flight 1549 into the icy Hudson River on Jan. 15 illustrates, the cost of mid-air collisions between birds and aircraft can and does affect the bottom line of aircraft operators.

While the National Transportation Safety Board (NTSB) continues to investigate the loss of the Airbus A-320 (N106US) minutes after it departed LaGuardia, it has already been established that the twinjet ingested a number of Canada geese that shut down both CFM-56 turbofans. Rory Kay, who is executive air safety chairman for the Air Line Pilots Association said it's "quite rare, but certainly not unheard of," for birds to shut down two engines of a plane.”

And the US Airways jet's dramatic splashdown in the Hudson wasn't the only near-tragedy caused by birds in recent months. A Ryanair 737-800 crashed at Rome's Ciampino Airport on Nov. 10 after it struck a massive flock of starlings and lost most of its engine power, according to the ANSV, the Italian accident investigation agency, and the airline.

New York area airports are no stranger to in-flight collisions with their feathered friends. There is a history of airliners departing Kennedy International ingesting sea gulls. In December 2006, for example, a great blue heron was sucked into one of two engines powering a Boeing 767 shortly after takeoff. Fortunately, the jetliner safely returned to the airport.

There was another incident at La Guardia as recently as 2003, when an American Airlines Fokker 100 reportedly hit a flock of geese upon takeoff, causing the right engine to fail. The flight was diverted to Kennedy.

Passenger aircraft are not the only victims of bird strikes. For example, the NTSB’s investigation into the Oct. 23, 2007 night training accident shows that a Canada goose collided with a Piper PA-44 (N327ND), killing the two pilots aboard. And, circulating around the web, are grizzly pictures of bird strikes against everything from passengers cars, trucks and trains complete with complete carcasses dangling from vehicle windows.

As for the Piper, the airplane was in cruise flight at 4,500 feet mean sea level (msl) when the airplane abruptly departed controlled flight and impacted a bog. A post accident examination of the debris showed that the left half of the horizontal stabilizer was bent upward approximately 90 degrees, inconsistent with the damage to the remainder of the airframe. This damage was consistent with the initial left yaw and nose down pitch recorded during the upset.

A depression and tear were observed on the upper wing skin near the left wing tip. Microscopic examination and DNA testing by forensic ornithologists identified the material on the wing skin section as remains of a Canada goose.

The NTSB determined that the probable cause of the fatal accident was “an in-flight collision with at least one Canada goose, and the resulting damage to the left stabilizer that caused the airplane to become uncontrollable. Contributing to the accident was the night lighting condition, which precluded any possibility of the flight crew seeing the bird(s) prior to impact.”

Bird strikes are on the rise, said LeBoeuf , and present a serious safety issue. The crash of a USAF Boeing E-3B Airborne Warning and Control System plane in 1995 after takeoff from Elmendorf AFB, AK, painfully drove that point home. All 24 crewmembers died when the plane struck a flock of Canada geese just after takeoff.

The BASH program works to avert accidents like the one at Elmendorf AFB. Based on a system of "integrated pest management," it aims to keep air bases, airfields and the air space and ground in and around them free of birds and wildlife that can hamper aircraft operations, LeBoeuf said.

That's a challenge, he said, with more Canada geese taking up permanent residence in the United States, a burgeoning snow goose population and a comeback for the pelican population after DDT and other insecticides were banned.

But birds aren't the only problem, LeBoeuf said. He's seen it all: deer, coyotes, wild pigs and even alligators finding their way onto USAF flight lines. "They're mobile speed bumps, and aircraft don't take kindly to them," he said. Indeed, airports throughout the country have similar hazards and alligator wranglers are not uncommon visitors in visitors to Florida airports.

Since 2000, at least 486 commercial aircraft have collided with birds, according to the FAA. Of those incidents, 166 led to emergency landings and 66 resulted in aborted takeoffs. Fortunately, wildlife strikes resulting in serious consequences for commercial aircraft are very rare.

According to FAA statistics, over 87 percent of reported wildlife strikes between 1990 and 2007 had no effect on flight. Pilots reporting an effect on flight most commonly performed precautionary landings to ensure the aircraft had not been damaged by the strike.

During that period, FAA received reports of 43 aircraft hull losses — which include aircraft that crashed as well as those that were damaged beyond repair — as a result of wildlife strikes. Only two of these hull losses involved commercial aircraft. Over that same time, 840 million landings and takeoffs took place, representing one aircraft lost for every 1.9 million landings and takeoffs.

Injuries and fatalities caused by wildlife strikes are also very rare; 197 injuries and 16 fatalities were attributed to wildlife strikes between 1990 and 2008. During this same period, there were over 12 billion commercial passengers enplaned in the U.S. The risk of being injured due to wildlife strikes is less than 1 in 50 million and the risk of being killed due to a wildlife strike is less than 1 in 750 million. These risks are even lower if one considers passengers that were enplaned on non-commercial flights. Still, the Bird Strike Committee said 219 people have been killed worldwide as a result of wildlife strikes since 1988

Meanwhile, the costs of U.S. airport wildlife management programs vary considerably from airport to airport. Depending on their size, location, and surrounding habitats, some of airports spend $250,000 or more per year on their programs.

Funds from the FAA’s Airport Improvement Program can be used to pay for a portion of costs associated with habitat modification projects and wildlife management equipment. However, staff costs, contractor fees, and other operating expenses associated with wildlife management programs are typically not eligible for federal funding and are borne by airports themselves.

The most deadly crash involving a bird strike occurred in 1962, when 62 people were killed on an Eastern Air Lines aircraft that crashed after takeoff from Boston. That plane collided with a flock of starlings, sucking the birds into three of its four engines, causing the plane to stall and plunge into Boston Harbor.

Commercial airline crews have reported at least 26 emergency landings, aborted takeoffs, or other incidents due to collisions with birds since January 2007, according to an Associated Press review of reports filed voluntarily with NASA's confidential Aviation Safety Reporting System.

In some cases, the aircraft's brakes caught fire or cabins and cockpits filled with smoke and the stench of burning birds. Engines failed and fan blades broke. In one case, a bird strike left a 12-inch hole in a Boeing 757-200's wing.

Among other cases detailed in the NASA database:

• In June 2007, a Boeing 757-200 at Denver International had to abort a takeoff after birds the size of grapefruit flew into its path. Birds were sucked into both engines.

• In July 2008, the pilot of a Boeing 737-300 in the midst of a takeoff roll spotted a hawk with a four-foot wingspan on the runway. As the bird flew past the left side of the plane, the crew heard a "very loud bang," and there was engine surge. The pilot aborted the takeoff at great strain to the aircraft's brakes, which caught fire. Fire trucks doused the flames. No one was hurt.