Short staffing among U.S. customs agents could mean longer lines for international air passengers this summer, causing more fliers to miss connecting flights.

With major airlines boosting international flights this summer, officials from New York John F. Kennedy, Newark, Washington Dulles and Los Angeles airports say they are worried about long processing lines for incoming international passengers. Customs and Border Protection says it hired all the agents for which it's budgeted.

At Washington Dulles, airport chief Jim Bennett expects to have 2005 levels of customs staffing, despite 18 percent growth since then in seats on international flights.

"They're not adding resources at anywhere near the pace to keep track with growth," says Bennett, CEO of the Metropolitan Washington Airports Authority.

Wait times at Dulles are up already. At the airport's biggest customs facility, the average wait during peak periods reached 68 minutes this month, up from a high of 57 minutes last summer, according to the customs Web site.

With much new international service at JFK and Newark, William DeCota, aviation director at the Port Authority of New York and New Jersey, says he's leery about summer lines because "staffing has always been tight." Maximum waits at JFK stretched as long as 2 1/2 hours last summer.

Since customs can't ramp up staffing this summer, DeCota hopes the agency will rush technology to automate some processing.

Customs officials say they're doing all they can, given roughly the same workforce as last summer.

"We don't want people waiting, either," says Robert Jacksta, the agency's chief of traveler security.

Some older checkpoint facilities were built to process 1,000 people an hour but, because of airline scheduling, receive three times as many at peak hours, he says.

To stretch resources, Jacksta says more overtime was approved for this summer compared with last summer. Some agents also can shift from seaports to airports, if necessary. The agency tries to keep average waits at or below 45 minutes.

Jacksta says he's also asked major airlines to shift arrival times to ease bottlenecks during peak periods, when lines are longest. American says it has spread out flights at its Miami hub, which should help previous problems at checkpoints.

He says he's asked American, United, Continental and Delta for help to minimize checkpoint bottlenecks.

At Los Angeles International, processing waits recently have forced passengers to sometimes be held on the plane for 30 minutes, says airport spokesman Paul Haney, "a situation not seen since the peak travel season of 2000."

Passenger Graham Cundick, 40, who lives in London but has a U.S. passport, found the lines at JFK horrendous when he traveled to the United States on May 3.

"It took an hour to get through immigration and customs," he says. "There weren't enough people, maybe four officers. It's not very welcoming at all, even if you are an American citizen."

Tourism officials fear a situation where stressed-out customs agents could treat tourists rudely.

"We can't confuse long lines and waits with great security," says Roger Dow of the Travel Industry Association, which wants Congress to add 200 more agents at airports.

But Colleen Kelley, president of the National Treasury Employees Union, which represents agents, believes "several thousand" more agents are needed at airports to alleviate lines and lift morale.

The Travel Industry Association is lobbying to get average processing times down to 30 minutes, instead of about 45 minutes at many customs facilities during peak times.