For the first time in a decade, a runway at Philadelphia International Airport has been lengthened to accommodate bigger jets and help reduce delays.

The project to add 1,040 feet to north-south Runway 17-35 is complete, and it got a green light from the Federal Aviation Administration and went into service Feb. 12.

The $70 million project began in the summer of 2006 and involved demolition of a service station, rerouting part of State Route 291, and reconfiguring the economy parking lot.

Now that the runway has been increased to 6,500 feet, it can be used by larger aircraft to ease congestion at one of the nation's busiest airfields.

When the runway was 5,460 feet, turboprop airplanes and smaller regional jets landed there. With the addition of 640 feet on the north end and 400 feet on the south, larger Boeing 737s flown by Southwest Airlines Co. and Airbus A320s operated by US Airways Group Inc. now land and take off there. Those planes previously used the main east-west runways.

Airport planners have estimated that flight delays will be cut about 8 percent now.

Since the longer runway opened last month, about 160 planes arrive on it daily, compared with 125 a year ago.

"The runway, on average, is getting about 22 percent more activity than it did in February last year," said Mark E. Gale, the city's acting aviation director.

Stretching from the economy parking lot on the north toward the Delaware River on the south, the lengthened 17-35 is part of a master plan that would also revamp two of the airport's four other runways over 20 to 25 years and construct a fifth, 9,100-foot runway.

"The first order of priority is to get the new runway along the Delaware River where UPS is," Gale said.

The city is in discussions with UPS Inc., which owns land and a building where the airport wants to put a fifth runway. City officials want to relocate UPS to another site nearby.

The FAA is expected to decide the fate of the project by early next year.

Then it would take 10 years to relocate UPS and construct the runway and connecting taxiways, Gale said. The new runway would be parallel to two other runways near the river.

The airport is the 10th busiest in the world, with 492,038 takeoffs and landings last year. Planners have forecast that number could reach 650,000 to 700,000 by 2025.

The airport is crammed onto 2,400 acres and has four runways - the newly expanded 17-35; two east-west runways known as 9Right-27Left and 9Left-27Right, and a 5,000-foot strip, known as Runway 8-26, used by corporate and private planes.

The last new runway - 8-26 - opened in 1999.

Airport projects take years of planning, environmental studies, and approvals.

In March 2005, the FAA gave final approval to extend Runway 17-35. The FAA and the state picked up most of the tab.

During a series of FAA hearings, the plan ran into widespread opposition from neighbors who said a longer runway would create more jet noise and air pollution.

The FAA determined in an environmental-impact statement that noise would increase only minimally over levels normally heard in neighborhoods.

Extending the runway required permanently closing a portion of Route 291, also known as the Industrial Highway, with traffic rerouted onto Bartram Avenue. At the same time, 300 parking spots in the economy lot were eliminated. An Exxon service station, at Route 291 and Island Avenue, was torn down, and that land used for 322 parking spots.

Demolition of the Overseas Terminal, used by international passengers until 1991, gave the city room for 800 more parking spots, which will be ready at the end of June.

A seven-lane toll plaza on Island Avenue, scheduled to open in May, will be a new entrance and exit to the economy lot. Cars will still be able to enter the lot near Terminal F but will have to leave on Island Avenue.

The airport, squeezed between New York; Newark, N.J.; Baltimore; and Washington flight patterns, suffers from chronic flight delays.

Philadelphia finished 26th last year among the 32 largest airports in on-time arrivals, at 73.01 percent, and 22d for on-time departures, at 76.93 percent, according to federal transportation statistics.

"The new runway is absolutely critical," Gale said. "Otherwise, forecasts show that planes are going to continue to come to Philly and the delay numbers are going to continue to grow."