NEW YORK — The collision of a sightseeing helicopter and a small plane over New York's Hudson River has intensified pressure to tighten the rules governing one of the world's most crowded air corridors — a largely unregulated airspace some pilots compare to the Wild West.

Among the ideas to improve safety: Assigning low-flying aircraft different altitudes, requiring them to carry collision-avoidance equipment or completely closing the area over the river.

"You don't have the concentrated levels of traffic anywhere else. There is no getting around it that the New York airspace is one of the busiest airspaces in the world," said Matt Zuccaro, president of the Helicopter Association International union.

According to the National Transportation Safety Board, about 225 aircraft fly each day within three miles of where a private plane crashed into a tourist helicopter on Saturday. Nine people were killed.

The planes all fly at or below 1,100 feet, where air traffic controllers cannot track them, and pilots are left to navigate on their own. Air traffic controllers do not attempt to separate aircraft. It's up to pilots to avoid collisions, primarily by looking out the window.

FLIGHT BAN CALLED FOR

U.S. Rep. Jerrold Nadler, a New York Democrat, yesterday urged the Federal Aviation Administration to ban flights by small aircraft unless they are equipped with collision-avoidance systems and transponders that report altitude and identification. He also said the planes should be required to file flight plans like larger commercial aircraft.

"It is unconscionable that the FAA permits unregulated flights in a crowded airspace in a major metropolitan area," Nadler said. "The Hudson River flight corridor must not continue to be the Wild West."

A report issued last month by the Department of Transportation's inspector general was sharply critical of the FAA for not implementing safety improvements that the agency had recommended, such as requiring cockpit voice recorders in smaller planes.

The report said aircraft that carry 30 or fewer passengers have a fatal accident rate 50 times higher than commercial air carriers. The smaller planes range from two-seat, piston-engine aircraft to turboprops, jets and helicopters.

An FAA spokeswoman did not immediately return a message seeking comment yesterday.

'PREVENTABLE' ACCIDENT

Dan Rose, an aviation lawyer and private pilot who frequently flies the Hudson River corridor, said the collision-avoidance system referenced by Nadler is "virtually standard" in new aircraft, helping to avoid collisions by showing pilots nearby aircraft on a screen.

"If it was on the helicopter, I think this would have been a preventable accident," he said.

Without a warning system, pilots must maintain their separation by watching the skies and listening for each other's radio communications.

Zuccaro, a former air tour company manager who has been flying helicopters in the Hudson corridor for 30 years, said despite the challenges, the corridor is generally safe.

"I wouldn't go in there unless I thought it was safe, and the same is true with the other pilots, fixed-wing and helicopter," Zuccaro said.

Mayor Michael Bloomberg has said the collision should not hamper the city's lucrative tourism industry.

The sightseeing helicopter that crashed is owned by a company that often charges $200 per person for a 12-minute ride. Since 2006, the FAA has regulated low-flying aircraft on the East River, where New York Yankees pitcher Cory Lidle and his flight instructor were killed in a crash.

"If they were to try to do that on the Hudson, I don't know where they're going to get the resources," the mayor said yesterday.

Using air traffic controllers to regulate all those flights would burden LaGuardia and Newark (N.J.) airports and cost money, he said.

AIRSPACE HEARINGS URGED

Former NTSB Chairman Jim Hall said the NTSB should hold hearings on airspace in the New York City area, similar to previous efforts to ease air traffic congestion in Hawai'i and around the Grand Canyon.

Accidents at the canyon have declined sharply since the FAA limited tours primarily to flying around the rims and over the top, rather than down inside, but air traffic remains heavy and unsupervised by controllers.

"It's still a risky environment," former NTSB member John Goglia said.

Hall said the New York airspace issue is "a problem that has been there and hasn't been addressed adequately from a safety standpoint."

"Having a tour operation in this corridor raises issues you just don't see in other parts of the country," he said.

Bloomberg, himself a private pilot, has said air traffic controllers may be able to monitor most of the traffic.

But "if you don't listen carefully and speak very quickly, this is not the place for you to fly. But if you have a lot of training, and you can handle it, there's no reason to think that you're not safe. Sadly, sometimes people make mistakes."