NEW YORK — Flying a small plane above the Hudson River can feel like ducking into a crowded, urban canyon — with towering skyscrapers on each side and more than a dozen helicopters and planes all buzzing lower than the nearby Empire State Building.
The city's worst air disaster in eight years has drawn calls for more regulation of the air corridor over the Hudson, which is less than three-quarters of a mile wide at the site where a helicopter and small plane collided midair. It serves as an air highway for helicopters, police patrols and small planes flown by pilots of varying ability.
"That's not a lot of space," said Ray Adams, president of the National Air Traffic Controllers Association union at Newark (N.J.) Liberty International Airport. "And it's not unusual at all for us to have 10 to 20 aircraft between the George Washington Bridge and the Statue of Liberty."
Divers pulled a helicopter and four more bodies out of the murky Hudson River on Sunday in their search for victims, wreckage and explanations from the midair collision of a sightseeing helicopter and a small plane that killed nine people.
The dead from Saturday's crash include three fathers and their three teenage sons. The private plane carried a family from Pennsylvania, and the helicopter held five Italian tourists celebrating a couple's 25th wedding anniversary.
The plane approached the helicopter, which had just taken off for a 12-minute tour, from behind and clipped it with a wing, witnesses said. Both aircraft split apart and fell into the river.
Searchers fought swift currents, dealt with visibility as low as one foot, and dodged debris dumped along the river bottom as they brought four more bodies on to boats. One was found in the fuselage of the helicopter, New Jersey State Police Sgt. Stephen Jones said. Two bodies remained missing.
A U.S. Army Corps of Engineers crane lifted the twisted wreckage of the helicopter from 30 feet of water. Nearby, a sonar scanner found the small plane wreckage, New York City police said. More plane wreckage was found farther out in the river under about 50 feet of water.
Pilots are largely free to choose their own route in New York, radioing their position periodically but not communicating regularly with air traffic controllers. Planes often fly as low as 500 feet to get a good look at the Statue of Liberty.
"So, what you have is a lot of helicopters. You've got the sightseeing tours. You have police helicopters. You have the weekend warriors who fly up and down the river," said Justin Green, an aviation attorney and former military pilot who has flown the route.
"All these airplanes are flying 1,000 feet or lower, and a lot of the pilots are up there to see the sights, so they may not be seeing and avoiding things as they should be," he said.
Pilots must stay under 1,100 feet to avoid straying into jetways used by commercial aircraft. They also aren't allowed to fly over Manhattan's tall buildings or stray into restricted zones around several major airports.
"What makes it kind of hairy is that, to stay out of all the restricted airspace ... you are kind of shooting the gap," Green said.
Planes and helicopters have blind spots just like cars do, making it difficult at times to spot an approaching aircraft, said Stanley Ferber, a flight instructor from Brooklyn.
"The only way to compensate is to have your head constantly on a swivel, moving your head around and scanning all parts of the sky," Ferber said.
In Saturday's deadly crash, the plane approached from the north and clipped the helicopter from behind, witnesses said. A warning from a pilot on the ground apparently came too late.
The collision may lead to the separation of helicopters and planes in the congested airspace above the New York City, said Hubert "Skip" Smith, an associate professor emeritus of aerospace engineering at Penn State University.
"There probably needs to be more regulation," Smith said. "Restricting the helicopters to 500 feet and below and having the airplanes fly between 500 and 1500 feet would probably help by separating these two distinctly different types of air traffic. I know that's what the helicopter pilots want."
U.S. Sen. Charles Schumer called for toughening flight restrictions over the Hudson, and New York City Council Member Gale Brewer said tourist helicopters should be banned from the corridor.
"All of us in this region also need to take a long and serious look at the circumstances surrounding this crash to ensure that significant air traffic over the Hudson doesn't come at the risk of the safety of New Jersey families who live along the riverfront," New Jersey Gov. Jon S. Corzine said.
The National Transportation Safety Board will look into the congestion issues, Chairman Debbie Hersman said Sunday.
But Mayor Michael Bloomberg, himself a recreational pilot, has argued that keeping the skies open to general aviation aircraft is necessary for the city's economy.
After Saturday's crash, he said that cutting off flights is "not something that anybody wants" and referred to the city's "commercial interests" in catering to the tour helicopters that take off daily from the West Side helipad.
Accidents are rare, he said, despite many daily flights. The city's heliports alone handle an estimated 88,000 takeoffs and landings a year.
"It is a crowded, busy area. And generally pilots that fly in this area are well trained and they certainly have plenty of practice," Bloomberg said. "When the roads are crowded and going fast, you really want to pay attention, and pilots here typically do."
But other accidents have happened in the crowded airspace around Manhattan. New York Yankees pitcher Cory Lidle and his flight instructor died in 2006 when they smashed into an apartment tower while flying a popular sightseeing route around Manhattan.
After that crash, federal officials banned all small, fixed-wing planes from flying over the East River unless the pilot had specific permission from air traffic controllers.