John Moot figured that whatever circling he would be doing yesterday would be on his descent into Boston. But here he was, stuck on terra firma, stopping, starting and reversing in a parking garage at Reagan National Airport looking for a space to land his Saab convertible.

He spotted one, at last, and with a squeal of tire against pavement zipped his car into it.

"This is the first time I've ever encountered this," said Moot, who flies from National every couple of weeks. "It's always been so convenient. I guess it's not so convenient anymore.

"If this is a regular problem, this will not be a good thing," he added, before rushing off to catch his flight.

It might well be a regular problem at National, where the 7,500 parking spots were filled yesterday for the fourth time this year. Airport officials said they expect to be at capacity again today despite using about 100 employee spaces to handle the rush of passengers.

The long lines of cars and anxious passengers coming out of them were the latest sign that airport traffic -- and all of its attendant problems -- has returned to pre-Sept. 11, 2001, levels. After years of focusing on security issues, airport managers are being reminded of the challenges they faced before the terrorist attacks: a shortage of parking, busy terminals and long ticket lines.

Washington Metropolitan Airports Authority spokesman Tom Sullivan said a lack of parking at National is "a good problem to have because it means traffic is back, but it also means airports are refocusing on capacity issues again."

Sullivan attributed the situation to a mix of business and leisure travelers that peaks on Wednesdays and Thursdays.

"What we're assuming is that business travelers are still out on business, and I guess it's one of the first weeks most school systems are out for summer, so we're really starting to see the start of summer travel," Sullivan said.

Airport officials have predicted that traffic at National will rebound to 15 million passengers this year, after dropping as low as 12.9 million in 2002. Similarly, traffic at Dulles International Airport is expected to come close to the 20 million mark, about where it was in 2000 before a low of 16.9 million last year, officials said.

Baltimore-Washington International Airport officials said the airport reached pre-Sept. 11 levels last year and has experienced a double-digit percentage increase in volume since then.

Parking problems have not extended to Dulles and BWI, both of which have added thousands of spaces in recent years. Dulles has 25,000 spots, and BWI has 30,000.

But National doesn't have the acreage that those two facilities do and has a limited ability to expand. Sullivan said that managers are looking for ways to add spaces, probably by adding parking decks to existing lots, but that there are no short-term fixes.

Sullivan said travelers to National should call 703-417-PARK (7275) to find out how many spaces are available. If there are fewer than 200, he recommended taking Metro, a taxi, a van service or a lift from a friend. If drivers get to the airport and find no spots, they'll have to wait because there is no off-site parking, Sullivan said.

That's exactly what some drivers were doing yesterday. They stared at red signs that said "FULL" as they lined up three and more deep waiting for the gates to rise so they could hunt for a spot. Some got frustrated and backed away, gambling that they would have better luck at another lot.

Jeff Stalnaker sat in his pickup for 15 minutes before he got through, then had to circle inside the garage a couple of times before finding a spot. He said he sat and waited because he had heard that the economy lot was full, too.

"I don't think I had much of a choice today," said Stalnaker, who was at National to pick up his mother. "I'm lucky I left a little early."

The Waldorf resident said parking was enough of a hassle that he would consider having his mother fly to BWI next time.

Over on the other side of the garage, James Jeffries was also searching for a spot, at one moment backing up his van in hopes of finding one and in the next speeding ahead in search of another.

Jeffries, a courier who goes to the airport three or four times a week, wasn't prepared to look for long. He gave up quickly and parked his van illegally on a crosswalk.

"This is the first time I've ever had a problem parking," he said before shrugging his shoulders and walking away.

The lots at Reagan National Airport filled yesterday for the fourth time this year and are expected to reach capacity again today.