National Transportation Safety Board (NTSB) investigators continue to probe the Aug. 8 mid-air collision of a Piper Saratoga and a sightseeing helicopter carrying a pilot and five Italian tourists over the Hudson River, killing all nine people aboard both aircraft.

The single-engine fixed wing PA-32R-300 ran into the rear of the Liberty Helicopter Tours Eurocopter AS 350 BA as the two aircraft were flying in the same direction. The fatal accident took place in a narrow corridor of airspace over the river reserved for aircraft operating under "see and avoid" rules. The Piper Saratoga, which had taken off from the Teterboro airport was heading south over the river to Ocean City, NJ. The helicopter, had just taken off from a heliport on the West Side of Manhattan.

Helicopter pilots and others who frequently fly the Hudson sightseeing route, which keeps them under 1,000 feet in altitude, rely on special operating procedures, including broadcasting on and monitoring of a dedicated radio frequency designed to make pilots aware of nearby traffic. Such transmissions are recommended but aren't required.

The mid-collision came less than a month after a federal watchdog agency warned that safety oversight of sightseeing and other for-hire flights is too lax.

The Department of Transportation (DOT) Inspector General (IG) report scrutinized the oversight of on-demand operators by the FAA.

According to the audit, there is less safety oversight of "on-demand" flight operators than commercial airlines.

On-demand operators include aerial sightseeing tours, and medical, cargo and unscheduled passenger flights of fewer than 30 people. The type of aircraft they use include small, fixed-wing planes, helicopters and larger turboprops and jets with 10 or more seats.

The FAA does not effectively inspect higher-risk on-demand operators and they do not have to meet many of the regulatory requirements that large, commercial air carriers must follow, the IG concluded.

The FAA hasn't implemented 16 National Transportation Safety Board (NTSB) recommendations aimed at improving the safety of on-demand flight operations or addressed recommendations made by its own advisory committee in 2005, some of which paralleled the NTSB urgings, the IG audit noted.

In 2007 and 2008, there were no commercial airline fatalities in the United States, but there were over 100 people killed in accidents involving on-demand flights,

IG auditors found that on-demand operators do not have to meet many of the regulatory requirements that large, commercial air carriers must follow. These operators also have more risk in their operating environments and receive less oversight from FAA. Further, the FAA does not effectively target inspections to higher-risk on-demand operators.

"The number of fatalities from on-demand operations makes it imperative that FAA address our recommendations, which focused on actions FAA needs to take to enhance safety and oversight of on-demand operators as it plans regulatory and oversight changes for this growing industry," the report stated.

One of the findings by the IG was that the FAA lacked a risk-based oversight strategy.

"FAA oversight of on-demand operators is based on compliance with regulations rather than where risk dictates. Conversely, FAA oversight of large, commercial air carriers is based on risk assessments. Prioritizing inspections based on areas of highest risk is essential for the efficient use of inspection staff and resources. FAA is developing a new risk-based oversight approach for on-demand operators; however, this new system is not scheduled for full deployment for at least four years," the IG report added.

The IG recommended that the FAA strengthen its oversight and implement a risk assessment oversight process for on-demand operators.

FAA spokeswoman Laura Brown said the agency agrees with the recommendations in the report, and is adjusting its oversight of on-demand operators to reflect the risk-based approach the inspector general is recommending.

Even as NTSB investigators begin to unravel the tragic sequence of events, the deadly accident has revved up debate over whether to restrict or perhaps even ban aircraft from flying low-level routes in airspace that rely solely on visual flight rules for aircraft separation.

A half-dozen elected officials lined up along the Hudson River in the aftermath and called for changes in how the airspace above the river is controlled in the aftermath of the fatal mid-air collision.

A letter sent to FAA Administrator Randy Babbitt by 15 members of Congress, requests immediate restrictions on New York City's airspace.

The letter says, in part:

"We write to request that the Federal Aviation Administration (FAA) immediately regulate New York City's congested and dangerous airspace. Saturday's midair crash between a sightseeing helicopter and a small airplane over the Hudson River is a tragic and powerful reminder of what we have known for some time - that the virtually nonexistent oversight of small on-demand aircraft must come to an end, particularly in New York's heavily congested airspace. The Hudson River flight corridor must not continue to be the Wild West. The FAA must act immediately, before further lives are lost.

"It is unfortunate that the FAA insisted to us for years that it lacked statutory authority to regulate the airspace in the New York City corridor below 1,100 feet altitude. We are gratified, that yesterday [Monday], the FAA reversed its position and agreed it has statutory authority to regulate this airspace. It is tragic that it took nine deaths to produce this belated concession. Now, the FAA should swiftly use its authority to prevent future tragedies," the letter stated.

The lawmakers said the FAA should take immediate steps to implement the recommendations of the DOT IG, the NTSB, and an FAA Advisory Committee for these types of aircraft operations. "At a minimum, the FAA must require the installation of the Traffic Collision Avoidance System (TCAS-II), and a Mode C Transponder, on all aircraft that seat less than 10 people. Any additional common-sense measures that can be implemented should be done so immediately."

They also said: "the FAA should carefully review this incident, along with other factors, and determine what additional improvements can be made in the near term and long term to improve the management of the region's airspace. For example, the FAA should examine the feasibility of moving to a satellite-based system for air traffic management that could provide greater technological capability to manage flight traffic below 1,500 feet. In the meantime, every helicopter and general aviation aircraft should be required to file flight plans, even for trips under 1,100 feet. In addition, we should seriously consider banning all flights below 1,100 feet until radar systems are available to track them."

Furthermore, the legislators said: "The Hudson River flight corridor presents unique challenges, but the danger of unregulated on-demand aircraft is also a widespread problem in the New York region and the country."

Meanwhile, the FAA on Aug. 13 suspended two air traffic controllers at Teterboro Airport who were on duty when the Piper collided with the helicopter over the Hudson River.

One of the two unidentified employees was the air traffic controller who handled the Saratoga flight but was on the phone "involved in apparently inappropriate conversations" at the time of the accident, the Federal Aviation Administration said in a statement. The second was the traffic controller's supervisor, who was supposed to be present, but was out of the building at the time, the agency.

FAA officials said, however, that they do not believe the employees' conduct had any role in the collision. "While we have no reason to believe at this time that these actions contributed to the accident," the F.A.A. said, "this kind of conduct is unacceptable, and we have placed the employees on administrative leave with pay and have begun disciplinary proceedings."

The National Air Traffic Controllers Association, the labor union representing FAA controllers, said in a statement: "We support that any such allegation is fully investigated before there is a rush to judgment about the behavior of any controller."

National Air Transportation Association (NATA) President James K. Coyne said "While such events are extremely rare, they do create an intense focus on the operations involved and can, unfortunately, lead to an environment ripe with speculation and misinformation."

NATA is concerned with the intense scrutiny being placed on the airspace in which general aviation aircraft operate in the New York City area, as well as the correlations being drawn between the fact that the helicopter involved belongs to a commercial air tour operator and the recent report issued by the Department of Transportation (DOT) Inspector General (IG) criticizing oversight of on-demand operations, such as air tours.

The characterization of the airspace as devoid of regulation is inaccurate. The airspace being referred to as "uncontrolled" only indicates that there is no active radar-based control of flights. Operations in this airspace are still subject to numerous regulatory requirements.

While the IG report highlighted the differences between regulation and oversight of the airlines and on-demand operations it failed to acknowledge the necessity of differing regulations due to the fact that on-demand operations comprise a vast number of mission profiles and include nearly every size and type of airplane and helicopter.

"There is much work to be done by the National Transportation Safety Board investigators to determine the facts of what happened," said Coyne. "Regulators and elected officials should reflect upon the outcome of the investigation rather than react to hypothetical scenarios."

At this time there is no indication from the National Transportation Safety Board (NTSB) that the FAA's oversight of the air tour operator was in any way related to the tragedy that occurred.

"Certainly the NTSB will look at all facets of the operation of both the airplane and helicopter to determine what facts may be relevant to the investigation. But, until the NTSB releases their findings, I believe it is imperative that we follow the advice of New York City Mayor Michael Bloomberg and avoid unnecessary speculation," Coyne concluded.