Hundreds of employees at the Port Authority of New York & New Jersey are leaving the agency this month under an early retirement program designed to

cut costs.

More than 250 staffers, most of them with more than 20 years' experience, already have told the agency they plan to take advantage of the incentive program. Thursday is the deadline for signing up."We're losing a lot of talented people with a lot of knowledge and a lot of history," said Frank Caggiano, deputy director of the port department. ''There's still a lot of talented people here, and they're going to have to step up."

Some executives expressed concern about the loss of institutional memory with exodus of experienced executives.

"Once you lose historical perspective, the future becomes less clear," said Roger Nortillo, executive vice president of Maher Terminals, the port's largest terminal operator.

Neil Goldstein, chief of staff for Rep. Jerrold Nadler, a New York Democrat and longtime critic of the port authority, expressed hope that the turnover would help an agency he described as "hidebound, lethargic and slow to move." That, he said, "is why the port has lost market share."

As a result of the early retirement program, the port department will lose at least 12 of its 300 employees, including Bob Goode, manager of planning; Jim Malone, general manager of port operations; and Jack Savage, former general manager of marketing and sales.

"I'm really concerned. This is an important agency doing important work. It's going to make the accomplishment of that work much more difficult," Mr. Savage, 55, said Friday, his last day at the port authority after 33 years.

Other senior executives who are retiring include Gene Fasullo, director of engineering; Mark Marchese, director of media relations; and Salvatore Samperi, deputy director of the agency's 1,400-member police force.

"I'm going to exchange my cellular phone for a fly rod," Mr. Marchese quipped.

The agency, which had some 9,100 employees before the retirements, is by far the nation's largest port authority. Besides marine terminals, its facilities include the World Trade Center; three major airports - John F. Kennedy International, Newark International and LaGuardia; six bridges and tunnels connecting the two states; and a commuter rail line.

The voluntary exodus is prompted by employees' fears of layoffs as the agency goes ahead with plans to cut spending.

Kathleen Donovan, chairman of the bi-state agency, said there will be no decisions on layoffs or other changes until Sept. 29. Like Mr. Fasullo, who directed the rebuilding of the World Trade Center's infrastructure after it was severely damaged by a terrorist bomb on Feb. 26, 1993, she insisted that the departures will not affect its ability to do its job.

"It will have no impact at all other than the personal impact of losing many good people. For the institution itself, we have so many talented people that there won't even be a blip in service. You miss the people, but the institution goes on," she said.

It will go on but as a much tighter unit under Ms. Donovan and George Marlin, the latter appointed by New York Gov. George Pataki earlier this year as its new executive director. Mr. Marlin has expressed interest in farming out some of the port authority's functions to the private sector, including some airport operations not already in private hands, and in selling the Vista Hotel at the World Trade Center.

The special retirement plan provides an extra month of credit to the employee's pension for each year of service. Thus, an employee aged 55 with 25 years of experience would be given credit for 27 years. Exact benefits depend upon the employee's level and the options he chooses. If, for example, he chose no survivor benefits, an employee could receive a pension equal to 54 percent of his final average salary for the last three years.

"I really loved the port authority. It's a very unique agency - the only one of of its kind to do so much for the region. I feel that's being emasculated," said Herb Ouida, who retired Aug. 4 as manager of regional export development in the port department. Mr. Ouida, who previously served as director of Xport, the agency's trading company, is now a consultant to the World Trade Centers Association.