A ruling by a U.S. Federal Judge in New York Tuesday has opened the door for hundreds of potential lawsuits against airlines, airplane manufacturers and the operators of the World Trade Center for the September 11 terrorist attacks.

U.S. District Judge Alvin Hellerstein ruled that litigation brought by people injured in the attacks and relatives of victims can proceed.

He indicated that airlines' alleged negligence in security screening could have contributed to the attacks two years ago. About 3,000 people died in the attacks, which took place after hijackers seized control of four planes on September 11, 2001. Two of the planes hit the World Trade Center in New York, and a third hit the Pentagon. A fourth crashed in a field in Pennsylvania.

The judge was ruling on 70 cases brought by the injured and representatives of people killed in the attacks and about 10 groups that suffered property damage.

The plaintiffs charged that the airlines were negligent in their failure to apply adequate security measures that would have prevented the hijackers from entering the cockpits and taking control of the planes.

They also accuse the owners and operators of the World Trade Center of negligence for the design of the towers and the inadequacy of evacuation routes.

The defendants include the companies that own American and United Airlines, airplane-maker Boeing, and the Port Authority of New York and New Jersey, which operated the World Trade Center.

The airlines argue that they could not be expected to predict the suicide hijackers' attacks and that they had followed federal safety standards at the time.

Officials and relatives of victims were closely watching the Judge Hellerstein's decision as the deadline approaches to apply for a federal compensation fund, which protects the airlines from lawsuits.

Relatives of people killed or injured in the attacks have until December 22 to enroll with the fund, created by the U.S. Congress. Anyone who applies also agrees not to sue the airlines, government agencies and security companies.

More than 1,500 families have yet to decide whether to accept federal compensation or pursue litigation.