It's summer in the city, almost, and US Airways' largest international gateway at Philadelphia International Airport is gearing up.

Flights to five seasonal destinations - Athens, Glasgow, Venice, Barcelona, and Lisbon - recently took off. On May 23, Shannon, in Ireland, and Edinburgh will launch.

Frankfurt is getting a second daily US Airways flight on Thursday. That is in addition to Lufthansa Airlines' year-round service to Frankfurt.

This summer, US Airways will have 20 daily departures to 19 cities in Europe and the Middle East, plus flights to the Caribbean, Mexico, and Canada.

US Airways will operate 486 flights on peak days, up from an average 429 in January, and more summer flights than last year. A second "red-eye" overnight flight from Los Angeles will be added, and extra flights for the summer to Sacramento, Seattle, and Denver.

Already, airplanes are fuller and lines a little longer at U.S. Customs and Border Protection. The summer crunch will be in full throttle when schools let out next month and families travel.

"The past six weeks, it's like it is summer already," said flight attendant Linda McPike, cabin service director on the flight to Barcelona on Monday. "The terminal is busy. The flights are full."

Historically, seasonal flights began in late April or May. Because of increased demand and bookings, several started earlier.

"It's our bread and butter in the summer, the transatlantic," US Airways spokesman Todd Lehmacher said. "It's no secret. It's a profitable operation for the company."

Inbound flights from Europe arrive at 12:30 or 1 p.m. through midafternoon. Most trans-Atlantic flights leave between 6:15 and 6:45 p.m., with the final two, to Tel Aviv and London Heathrow, after 9 p.m. British Airways has two evening flights to London.

Delta operates a summer-only flight to Paris. Frontier Airlines flies charters to the Caribbean and Mexico for Apple Vacations. Air Canada has four daily flights to Toronto.

At the US Airways hub control center, a glass tower above the international terminal, fleet managers instruct arriving planes which gate to go to, and tell pilots parked at gates when to push back to leave.

"We handle the stuff on the ground; the FAA handles them in the air," said Donald "D.J." Westbrook, who oversees the operation.

On Monday, the skies were partly sunny, and the winds light and variable. At noon, 14 flights were in the air coming from Europe. Most were 15 to 75 minutes early due to favorable winds.

At the hub control tower, Westbrook and Philip Moore, a senior manager, watched dots on a computer screen, each representing a wide-body airplane crossing the Atlantic over Newfoundland and down the U.S. coastline to Philadelphia. The tower monitors aircraft movement 24/7 around the terminals, handing off planes to Federal Aviation Administration air traffic control, located in a separate tower across the airfield. Air traffic control, in turn, hands off planes to ramp controllers who direct aircraft for all the airlines, not just US Airways and American.

The first international flights arrive from Tel Aviv at 5:20 a.m. and from Doha in the Persian Gulf on Qatar Airways, at 7:30 a.m. After 12:30 p.m., it is a conga line of transatlantic arrivals.

On Monday, most flights from Europe landed early. Passengers swelled lines at U.S. Customs, whose goal is to keep Philadelphia passenger waits under an hour. That contrasts with three-hour waits in Miami and New York Kennedy airports last summer.

During peak arrivals, Customs in Philadelphia will have 20 officers on the line, said public affairs officer Stephen Sapp. Depending on the mix of foreign nationals and U.S. citizens, "we readjust officers in booths to handle them," he said.

To clear travelers faster, Philadelphia airport will soon get automated passport "self-help" kiosks. U.S. citizens swipe their passport into the kiosk and answer questions normally a customs official would ask. The passenger still sees a customs officer to verify some information, but the kiosk speeds the process.

"We recommended 24 kiosks, and we expect to have them by mid-June," said Joe Taney, US Airways and American's vice president of operations in Philadelphia.

"Anything we can do to improve the process" and cut a 60-minute wait to 30 minutes "will help the experience of all customers," Taney said. At U.S. airports such as Chicago O'Hare, the kiosks "have improved the processing time immensely."

Ninety minutes before every international flight, pilots and flight attendants meet to discuss the route, weather, and any concerns. International routes are coveted and go to the most senior crews.

On the 6:45 p.m. flight Monday to Barcelona, three pilots and nine flight attendants introduced themselves. For seven hours, they and 140 passengers would cross the ocean, with no radar coverage to land.

"The most important thing, if you are not happy with something, I'm not happy," said Capt. Doug Burke, a pilot for 36 years, who briefed the cabin crew. "Safety is the primary concern. If you need anything, please yell for us, and let us know."

Earlier, the pilots - Burke, Jim Hunt, and Bob Gilmore - mapped the course across the Atlantic that included plotting three "alternates" to ensure that the plane would be no farther than 120 minutes from a place to land.

Aircraft flying across the Atlantic follow tracks because there is no radar. Flight plans are generated by an operations control center in Pittsburgh. Pilots compare and check a map. "We're following that little line," said Burke, who telephoned a dispatcher in Pittsburgh.

"I gave you extra fuel," the dispatcher said. In case the plane needed to divert because of turbulence, "you'll have some fuel there to work with."

"We're good on everything. I'm happy with the fuel, so thank you," Burke replied. Soon after, the crew boarded the Airbus 330 to Barcelona.