Domestic travel might be in a slump, but overseas flights are surging at Los Angeles International Airport.

Foreign airlines are turning to LAX again despite crowded, aging terminals -- frequent-flier surveys often rank it among the nation's worst -- that have made it the bane of airlines and passengers.

While U.S. carriers are cutting back amid a slowing economy and high fuel costs, international airlines are flocking to LAX as more overseas travelers look to take advantage of the weak dollar.

Fares are likely to remain high as long as oil prices stay at their current levels, but the upswing in overseas flights could provide relief to some of the more-popular destinations in Europe, South America and Asia. And with the number of nonstop flights growing, people on international flights can look forward to reaching their destinations faster.

The boom is raising worries of overcrowding and long lines at U.S. Customs and Border Protection checkpoints, which some critics say are already understaffed. LAX is the nation's second busiest for international flights.

Paul Haney, the airport's deputy executive director, said he hadn't seen so many new international flights being added at LAX in at least a decade. "It seems the marketplace is being somewhat forgiving of our infrastructure shortcomings," he said.

Eight carriers have started or announced new international service to LAX since October, including the first nonstop flights to Rome on Alitalia Airlines beginning in June and Air France nonstop service to London starting today.

Emirates Airlines, the world's fastest growing, announced this month that it would launch LAX-Dubai nonstop service, targeting Southern California's sizable Middle Eastern community.

Brazilian carrier OceanAir filed an application this month with the U.S. Department of Transportation to start its first U.S. service with nonstop flights between Sao Paulo and LAX. The carrier's Brazilian rival, TAM Airlines, also is eyeing the route.

Korean Air announced last week that it too would start nonstop flights between LAX and Sao Paulo. The service by the South Korean carrier would target business travelers in the U.S. as well as provide connecting service for Asian passengers who currently don't have nonstop flights to Brazil.

Other foreign carriers have been expanding service to Los Angeles. Qantas Airways said March 13 that it would add three more flights per week to Sydney and Brisbane, and Air China plans to add a second daily nonstop flight to Beijing this summer.

A new airline in Australia, a brainchild of British billionaire Richard Branson, is expected to announce today that it will begin nonstop flights from Sydney and other Australian cities to LAX in a direct competition with Qantas. The announcement is expected at the same time U.S. and Australia sign an accord allowing unrestricted flights between the two countries.

An all-business-class airline also is considering nonstop service between LAX and London, heating up the competition for one of the busiest and most-lucrative routes.

The latest surge in international service at LAX comes as a weakening dollar has fueled demand for flights to the U.S. from travelers overseas. At the same time, many of the nationalistic restrictions are being relaxed, allowing more flights between the U.S. and other countries. And after a hiatus, airlines are starting to get their long-awaited planes needed for the long-distance routes.

The bustle at the Tom Bradley International Terminal is in stark contrast to domestic traffic, which is expected to stay flat or decline as the economic downturn and higher air fares propelled by record fuel costs damp travel.

The international boom is helping LAX fend off competition from San Francisco and resurrect passenger traffic that slid sharply after the Sept. 11 terrorist attacks. Last year, several airlines began shifting some flights to San Francisco International Airport, where a spacious international terminal has been built.

But LAX officials forecast that the number of international passengers this year will be in the range of pre-9/11 levels. The number of international passengers was up more than 8% in January and nearly 11% in February.

It's the kind of uptick airport officials haven't seen since the Boeing 747-400 began entering service in 1989, giving international carriers an economical and profitable way to fly more people greater distances.

"It's going to be a very busy summer," said Frank Clark, executive director of LAXTEC Corp., the nonprofit group that represents airlines that fly out of the Bradley terminal.

Customs and Border Protection officials said they were "assessing the potential impact of the passenger traffic over the next few years" but didn't have plans to add staffing.

"We are going to do everything we can to manage it with what we have," said Michael Fleming, a spokesman for the agency's Los Angeles office.

The new flights are expected to have significant effect on Southern California's economy. A 2007 study by the Los Angeles County Economic Development Corp. estimated that one daily transpacific or transatlantic flight on a wide-body jet pumps about $620 million annually to the local economy and sustains 3,120 jobs directly and indirectly.

In all, LAX is expected to add about a dozen new long-haul flights that could pump more than $7 billion into the local economy.

Emirates' decision to fly to LAX was considered a key win by airport officials. San Francisco has been aggressively vying to unseat LAX as the West Coast hub for international flights.

Since several carriers shifted international flights to San Francisco last year, LAX has undergone a resurgence of its own after launching an aggressive marketing campaign and beginning Bradley terminal renovations, including adding several lounges for business- and first-class passengers.

But for Emirates and other foreign carriers starting service at LAX, the airport was chosen for a simple reason: Although San Francisco has better and newer facilities, LAX has the larger potential passenger market.

"It was clearly the next move for us because of the sheer size of the market," said Nigel Page, Emirates' senior vice president for commercial operations, the Americas. "We saw that there was a lot more potential there."

peter.pae@latimes.com