"All the doom and gloom turned out not to come out," he said. "And that's because we stuck to the program."

But already the average turnaround time to process a passport fee had grown from 24 hours to three weeks, as 2.1 million applications arrived in January — 600,000 more than expected. Citicorp, which processes the fees under a contract with the Treasury Department, added 400 workers to its already expanded staff of 800 to clear the backlog.

Instead of fixing the problem, however, that sent a tidal wave of paperwork downstream. "They were not handing [the applications] over on time, and then they dumped them on us all at once" in May, said Janelle Hironimus, a State Department spokeswoman.

Sheryl Morrow, director for the revenue collection group at the Treasury Department's Financial Management Service, countered that the State Department was well-aware of the backlog. "They get daily reports from the bank. They knew what was coming," she said.

Analysts at the State Department initially forecast that passport applications would increase from 12 million to 15 million annually under the new system, then upped the projection in 2006 to 16 million. Those estimates, Harty said Tuesday, were based on a study by BearingPoint, a consulting firm in McLean, Va.

When a heavier volume of applications came in — at the current pace of 17.5 million annually — the system was temporarily swamped, said Ann Barrett, deputy assistant secretary of State for passport services. "None of us has a crystal ball," she said.

According to the National Federation of Federal Employees, which represents passport office workers, the department had planned to almost double the number of employees, from 480 to 945. But only 218 new workers had been hired since 2005, the union said.

Barrett disputed those numbers, saying her office hired more than 250 employees and never promised more.

Officials within the travel industry — beset for months by panicked vacationers — say the State Department's miscalculation was drastic. "Clearly, they didn't hire enough," said Rick Webster, chief Washington lobbyist for the Travel Industry Assn. of America. "They simply asked for too little in terms of resources. They admit that, but they almost talk about it as if it was a factor of degrees. But it was a bigger miss than that."

Barrett announced plans this month to hire 400 more workers by October at a cost of $37 million, but screening and training them could take several months.

In the meantime, travelers are turning to their representatives and senators, hoping their intervention can help.

The office of Sen. Norm Coleman (R-Minn.) has handled more than 1,500 such requests since January. "The most frustrating thing for the constituents we talk to is that they are doing what the government told them" to do, said Luke Friedrich, Coleman's spokesman. "They applied early, following the guidelines the government set out for getting their passports on time. And the government, for some reason, wasn't ready."

If they can get an appointment, travelers scheduled to leave within two weeks or who need a foreign visa — and who have hours to devote to standing in line — can bring their applications to one of 14 passport agencies around the country. Even then, delays abound.

Carmen Diaz of Germantown, Md., applied weeks ago for passports for herself, her son and her daughter, whose soccer team is traveling to Brazil. With a deadline approaching for obtaining visas, she gave up checking the status of their applications online and came to Washington on Friday.

"They couldn't help me, because I wasn't leaving in the next 24 hours and they were only helping people who were leaving the next day or over the weekend," she said.

After hours in line, she got an appointment for Tuesday. But because the passport agency could not find some of her paperwork, she had to redo her three applications — including making a trip out of state to get a copy of her son's birth certificate.

California, with a large concentration of naturalized U.S. citizens, has been one of the areas hit hardest. Some of the longest lines have been at passport agencies in Los Angeles and San Francisco.

In addition to the staffing issue, the State Department also has faced questions about the planned expansion of its passport facilities.

In advance of the stricter travel regulations, the department opened one new passport agency in Aurora, Colo., in August 2005 and one new processing center in Hot Springs, Ark., this March. The Hot Springs center is expected to handle 10 million passports a year; so far, Harty said, it has processed 150,000.

Once the passport requirements are extended to land and sea travel, the State Department expects to receive 26 million applications — a 50% increase over the 2007 projection.