Updated

NEW YORK -- The U.S. government has struck a secret deal with operators of tourist helicopters, allowing them to fly in airspace over New York's Hudson River that is supposed to be reserved for small, private aircraft.

But private pilots who use the corridor are not being warned by Federal Aviation Administration (FAA) flight briefers to be on alert for the choppers.

Former National Transportation Safety Board chairman Jim Hall blasted the deal, noting, “Safety is best served when impactful decisions are made openly and with input from other agencies and the public -- not quietly and behind closed doors."

The change, he said, “adds unnecessary complication to an area that already has too much."

Ken Paskar, a Manhattan pilot and safety advocate, put it more bluntly, “You have hundreds of helicopters flying up and down through that airspace, and nobody knows about it ... it’s insane.”

The arrangement, reached without hearings or public announcements, gave helicopter tours access to the off-limits airspace via a “letter of agreement” signed by reps of five tour companies and two local FAA officials.

The pact -- a copy of which was obtained by the New York Post -- throws out key flight rules imposed over the Hudson after nine people died in an August 2009 midair collision between a plane and tourist helicopter.

After that disaster, the FAA gave “transient” aircraft flying above the river -- mostly single-engine, fixed-wing aircraft on sightseeing flights -- exclusive access to a corridor between 1,000 feet (305m) and 1,300 feet (396m) above the water.

“Local flights," primarily helicopters, got the airspace below 1,000 feet (305m). Flights in both corridors are generally not handled by controllers.

The new rule was lauded at the time by Transportation Secretary Ray LaHood, who said, “better separation of aircraft means a higher margin of safety."

But barely a year later, in August 2010, the FAA furtively changed the rules -- allowing two holes for choppers into the small-aircraft corridor.

The aim of the new setup is to give choppers access to altitudes above 1,300 feet (396m).

Tour operators sought the exception because of Manhattan residents’ noise complaints, said Jeffery Smith, chairman of the Eastern Region Helicopter Council.

Except to confirm the agreement’s details, the FAA declined comment.