The Federal Aviation Administration's database tracking bird strikes shows reports of collisions with geese and other large birds increased from an average of 323 a year in the 1990s to 524 per year from 2000 to 2007, a 62% surge.
These birds are big enough to potentially cripple a large jet.
The most serious reported cases in which large birds damaged aircraft also were up. Large birds damaged at least one engine on aircraft an average of 10 times a year in the 1990s. Since the year 2000, that number climbed to more than 12 per year.
The data, complete through 2007, come from records that the FAA has refused to release since a flock of Canada geese ruined the engines on a US Airways jet on Jan. 15. Last month, the aviation agency proposed permanently barring the data's release, maintaining that the records could be misleading and could prompt airports and others not to report bird incidents.
However, the agency acknowledged Monday that it had previously released the data to several individuals who had made requests under the Freedom of Information Act. Spokeswoman Laura Brown said that the agency had not denied a request for access to the data in the past.
Brown confirmed that the data show an increase in aircraft strikes involving large birds but said the risks to planes remains very low. "Significant strikes are still a very small part of the total bird strike numbers," she said.
Out of 58 million flights in 2007, there were 550 instances of aircraft hitting large birds and only 190 of the strikes caused damage. Even fewer, 15, caused damage to an aircraft's engine.
Two airline jets have been downed by birds since November, including the dramatic Hudson landing. In the second incident, a Ryanair jet in Rome struck a massive flock of starlings as it attempted to land on Nov. 10. No one died in the accidents.
The findings on large birds are a concern because their populations are increasing, said Richard Dolbeer, a retired Department of Agriculture wildlife biologist who created the FAA database in 1990.
"In most cases it's going to be these large birds that are going to cause a catastrophe or a significant strike event," Dolbeer said.
Most jet engines are not required to withstand an impact from a bird weighing more than 4 pounds, according to federal standards.
Wildlife experts such as Dolbeer have been raising concern about the surge in populations of geese, cormorants, pelicans and other large bird species in recent decades.
The database contains thousands of records a year. Most are relatively minor incidents, such as when planes hit tiny birds that pose little risk. But the data also contain hundreds of incidents in which serious damage to large jets was reported.
On Oct. 12, 2007, a Skywest Airlines CRJ-700 regional leaving from Denver International Airport struck a flock of as many as 100 sandhill cranes, large birds that weigh an average of 13 pounds.
After flying for about 20 miles, they hit the birds and the pilots felt several thuds. One of the engines began running rough and a pilot declared an emergency in a radio call to controllers. The pilot said "he didn't think he was going to be able to make it back to the airport," the FAA report said. The jet returned to Denver and no one was injured.
On Nov. 11, 2007, a Jetblue Airways Embraer EMB-190 jet flying at 4,000 feet as it headed toward John F. Kennedy International Airport in New York struck a large flock of Canada geese, the same type of bird that brought down the US Airways jet into the Hudson in January.
One of the jet's two engines was severely damaged, requiring a two-week repair, according to the database. "Plane looked bloody," the report said. "Cabin had horrible burning smell."
The FAA has estimated that only about 20% of the incidents involving birds are contained in the database because reporting bird strikes is voluntary. As a result, it's difficult to know the full extent of the risks that birds create.
The National Transportation Safety Board, which investigates accidents, urged the FAA in 1999 to require airports, airlines and others to report bird strikes. But the FAA has declined.