The Thursday after Hurricane Katrina hit, Eileen Thaden received a call from the Federal Emergency Management Agency: Could she be at the airport within an hour?

The 45-year-old Anne Arundel County resident had been expecting the call ever since she had signed up a year earlier to be a disaster assistance employee -- part of the surge force that the government has long relied on for extra manpower in emergencies.

Thaden had the desire and the skills to help. She had lost her own home in Hurricane Isabel, and she had spent two days at a FEMA training program where she learned how to assist other disaster victims. But now, faced with one of the largest disasters in U.S. history, she could not go.

Because of a bureaucratic foul-up she had been trying to resolve for months, FEMA had never issued her the special credit card that is the lifeline of any reservist. "I couldn't help," she said, "because they couldn't get their act together."

Although it is not known how many others are in Thaden's predicament, her experience showcases a reserve force that has been allowed to wither from inattention in recent years, according to former and current agency employees and outside experts. Its decline, they say, has contributed to the government's slow response to Katrina and has kept FEMA personnel stretched to the limits as the agency grapples with the aftermath of Hurricane Rita.

With a regular workforce of just about 2,500 full-time employees, the nation's lead disaster-response agency is not designed to have the personnel in-house to manage a disaster. The reservist program is intended to give it the ability to double or triple in size overnight by adding men and women who become, for as long as the disaster lasts, federal employees.

The reservists perform many of the same tasks as full-time FEMA workers, with each receiving training in a specific job, such as helping to run disaster response centers, inspecting damage, manning telephone hotlines, assisting victims with claims, and coordinating relief activities with state and local officials.

Historically, the reservist ranks have been heavily populated by young people who want to make money helping out in a time of crisis and retirees -- especially ex-government employees -- whose schedules allow them to walk away from their lives for weeks or months at a time.

Besides their training, reservists submit to fingerprinting and a background check and swear to uphold the Constitution. Each is paid based on a scale linked to education and experience levels.

In past emergencies, they have been at the heart of FEMA's response.

"If you were a disaster victim, you probably never met a FEMA employee. They were all [reservists]," said George Haddow, the agency's deputy chief of staff in the Clinton administration.

A FEMA budget fact sheet for fiscal 2005 listed its full-time staff at 2,511 and its "disaster staff" at 2,265. A FEMA spokeswoman said the reserve force numbered 5,000, though the agency did not respond to other requests for information about the force's use and trends in its size.

Some people with knowledge of the agency's workings say whatever the number, the role of the reservists has diminished. Haddow said he thinks the change has hurt FEMA's ability to respond to disaster because the reservist force included some of the agency's most knowledgeable people.

"It seems in the past few years that they've been using the contractors more and more, instead of reservists," Haddow said. "But they were an invaluable asset. All FEMA's senior staff put together doesn't have as much experience with disasters as a single one of them."

FEMA has come under intense criticism in recent weeks for not paying enough attention to how it would respond to natural disasters as its focus shifted in recent years to terrorism. James Lee Witt, President Bill Clinton's FEMA director, said in a 2002 memo that the agency had moved away from civil defense to beef up natural disaster resources in the 1990s. He feared the post-Sept. 11, 2001, emphasis on homeland security was "recreating that previous imbalance."

Several agency observers said the reserve force may have been a casualty of that latest transition.

Pleasant Mann, an emergency response specialist and former head of the union for headquarters employees at FEMA, said the database of available reservists was supposed to be replenished over the summer with additional names but never was.

At one point, Thaden said, she had even received a call telling her that FEMA had decided to deactivate her, as well as 2,000 more reservists who had received training around the same time. The agency later said that had been a mistake and that she was eligible to serve, though it still failed to get her a credit card.

Meanwhile, FEMA has had delays in dispatching many of the reservists now serving in the Gulf Coast. In previous years, reservists were sent directly to the scene of the disaster. This year they were sent to a few centralized staging areas such as Atlanta and Orlando to get refresher training, receive assignments and move on to the Gulf. But Mann said that took several days in some cases, wasting valuable time. "It was a hindrance," he said.

Since Katrina hit, FEMA has put out requests seeking additional reservists. "The work environment will be stressful and the hours long. Do not expect air conditioning or a room with a view," read one recent job posting. "Do expect a rewarding job experience, in public service to the communities and citizens rebuilding their lives."

Leo Bosner, Mann's successor as union president, said no matter how quickly FEMA can add new people, the agency's workforce is still stretched to the limits after four weeks of 12-hour shifts. And now with Rita, no relief is in sight. "We just don't have enough experienced people to go around," Bosner said.

Private contractors FEMA hires to help in the disaster response have also been seeking applicants at a furious pace.

The Fairfax-based engineering firm Dewberry, one of FEMA's biggest contractors, has been running advertisements in every major newspaper between Houston and Mobile, Ala., asking for applicants with experience in home inspections, engineering or public infrastructure. The company is seeking to add to its already substantial force of 2,500 workers stationed in the Gulf, according to executive vice president Larry Olinger.

Investigators looking into FEMA's response to last year's storms in Florida found that, because of lax oversight and inadequate training, some contractors working as FEMA inspectors gave out millions of dollars to people who were not financially affected by the storms and did not deserve the money.

Olinger said Dewberry, which was not involved in the Florida case, is taking steps to ensure its new hires are qualified.

"We feel that we're providing the right amount of training and the right amount of oversight," he said.

One former reservist who is heavily involved in the Katrina recovery said that is the danger of using contractors instead of reservists: "The contractors are scrambling to fill the slots, but you don't know if the people they hire are going to be qualified," she said, speaking on the condition of anonymity because she is not authorized to speak publicly on the issue. "When you use [reservists], at least you know that they're trained and they have the skills."

Besides the people it deploys to the disaster areas, FEMA has also been bringing in temporary workers to staff call centers that have been overwhelmed in recent weeks by victims dialing 800 numbers to file claims.

For FEMA's Hyattsville center, for example, Augmentation Inc. of Rockville recruited workers over the Internet and in brochures at churches, one company official said Thursday. One such ad cited pay from $15 an hour to $22.50 for overtime pay.

Augmentation has placed 700 temps and was planning to add another 240, the company official said.

The influx caused some confusion and consternation among the 200 or more workers usually at the call center site, according to one source familiar with the situation, who would talk only without being identified. At times, the newcomers from the temp agency did not have log-ons to enter the computer system and sat around doing nothing productive, this source said.

Staff writer Charles R. Babcock contributed to this article.

Eileen Thaden lost her home in Hurricane Isabel and became a reservist for FEMA. But she couldn't go to the Gulf because of a bureaucratic foul-up.