The airlines favor much of the plan, but not the proposed new, $1.9 billion runway, which they say won't seriously ease congestion and would be costly because it would require relocating and building a new United Parcel Service airfreight facility and in-filling acreage in the Delaware River.
Last year, airlines approved $734 million in capital improvements at the airport. The projects are in various stages of discussion, planning, design, and, soon, construction.
Here's a breakdown of what the airlines support:
Lengthen a main east-west runway by 1,500 feet to 12,000 feet, and improve taxiway and aircraft holding areas on the airfield to better queue planes for departure.
The taxiway work has been designed, and a construction contract will be awarded for work to begin this summer, said Chellie Cameron, deputy aviation director for finance and administration.
A design contract for the runway extension itself is "ready to be awarded. We would hope that construction could begin next year," Cameron said. Radar equipment will have to be moved, and "that work is out to bid."
Redesign the Terminal B and C ticketing areas, with new automated baggage handling and screening and a centralized, spacious passenger-security checkpoint.
US Airways and American want to manage the design and construction of what is the heart of their "mainline" operation. So far, the airport hasn't agreed "to relinquish all control of the design," Cameron said. "I'm hopeful in the next couple months we'll have the agreement finalized."
In 2007, airlines approved $40 million for the B-C Terminal design, and in 2013 authorized $200 million to begin construction.
Replace current rental-car surface lots with a multistory, consolidated rental-car building. It will require 18 to 24 months to work with rental car companies on a business agreement and design.
Perform initial design for an automated "people mover" to transport passengers between terminals, making it easier to connect to flights. "We are working through some concepts right now," Cameron said.
Make security upgrades, roof and window replacements, and improvements to escalators, restrooms, roadways, concessions, and flight-information displays. "We are either in design, out to bid, or in the process of awarding contracts for all the rehabilitation and repair work," Cameron said.
Separately, the city and airport recently announced an agreement to pay about $3 million a year - funded largely by the airlines - to neighboring Tinicum Township, Delaware County, and Interboro School District. Two-thirds of the airport is in Tinicum.
US Airways and American, which transport nearly 80 percent of air travelers in Philadelphia, reiterated concern Wednesday about the cost, and the timing of a new runway.
"Proceeding with implementation of the runway too soon would eliminate PHL's strategic cost advantage over other hubs in the region," said spokeswoman Andrea Huguely. "Moreover, a new runway will not solve the delay problem without significant airspace changes in the region. We continue to have discussions with the airport as well as other carriers that serve PHL on this important issue."
Airport CEO Mark Gale and Mayor Nutter have said the multi-billion-dollar expansion is critical to the economic health and growth of the region, and will create thousands of jobs.
"It's important for us to keep this program reasonable, and do projects when they are needed," Cameron said. "We want the costs to remain at a competitive level. That can only happen when you work in partnership with the airlines and figure out what makes sense in terms of timing and project scope at the time."