David and Goliath are at it again.

In this case, David is Tinicum Township, the Delaware County municipality where two-thirds of Philadelphia International Airport is situated, and Goliath is the city, the airport's owner and operator.

Tinicum and Philadelphia have been like cats and dogs for years over the airport's need to grow to meet the demand from airline passengers for more service, and how that expansion affects Tinicum residents and businesses.

Maybe that's unfair to cats and dogs, since in many homes they manage to peacefully coexist under the same roof. With these two, that doesn't seem likely to happen any time soon.

According to a lawsuit filed last week in Delaware County Court, David would suffer irreparable harm if Goliath and the Federal Aviation Administration are allowed to proceed with their "Capacity Enhancement Program."

That's government-speak for the long effort to try to cut down on flight delays caused by the airport's congested layout.

It's unclear whether this stone from David's slingshot will slay the giant (by the way, the David-vs.-Goliath cliche I picked up from the joint county-township news release on the suit), but it could slow down the expansion plan.

The suit asks the court to make Philadelphia seek the consent of Tinicum and the county before it buys any land for expansion.

If I lived in Tinicum, I would probably be cheering on the township and county. To "enhance capacity" at the airport, another runway would be needed along the Delaware River and other physical changes would be made to the current layout.

The big UPS package-sorting facility would have to be moved to a new location in the township. About 72 homes and 82 businesses would have to be relocated, reducing borough, county, and Interboro School District tax revenue and requiring it to be made up elsewhere.

The township and the county also said they believed that about 80 acres of wetlands along the river would be harmed by a new runway.

Delaware County already is in a separate fight with the FAA, trying to stop its airspace redesign program that has over the last 18 months changed aircraft takeoff paths so that more planes are flying over populated areas.

Needless to say, the county doesn't like much of anything about the FAA's conclusions in its environmental-impact statements, which say that airspace redesign or airport expansion will have only minimal effects on surrounding areas.

But try looking at this issue from the city's point of view. The airport, bearing the city's name, suffers from a poor reputation for on-time airline service. In 2005, it had the worst record in the country among the 31 major airports tracked by the U.S. Bureau of Transportation Statistics.

Despite significant improvement in on-time performance more recently, city leaders say that reputation has hurt Philadelphia's effort to attract visitors and to persuade businesses to locate here. It's embarrassing when the media (many times that's me) keep harping on it.

As air traffic grows, congestion and delays are expected to grow even more. That's why the city and the FAA have spent a decade exploring every way to improve the situation.

The suburbs and the city agree that the airport is one of the region's greatest economic engines, one that requires cooperation to fulfill its potential.

The suburbs, though, continue to use an unrealistic argument against the runway-building plans: Expand the meaning of the "region" by working to move air traffic away from Philadelphia and to smaller airports in Atlantic City, the Lehigh Valley, and Northeast Philadelphia.

But, as the FAA said in its environmental-impact statement on the Capacity Enhancement Program, "Airlines and air passengers decide on which airports to use based on market forces, and these decisions cannot be regulated by FAA or other government agencies."

In other words, encouraging travelers to use the smaller airports and seeking more service is well and good, but in a deregulated industry, airlines will concentrate their service at Philadelphia if that's what their customers want.

Perhaps the most important aspect of the lawsuit against the city is contained in what Michael Messina, president of the Tinicum Township Commissioners, said in the news release: Talk to us and show some respect.

"By asking for this declaratory judgment action, we are saying that Philadelphia must negotiate with the officials of Tinicum and Delaware County, and consider the residents they represent when they propose expanding the airport in our township," Messina said. "The FAA and the city can no longer run roughshod over Tinicum when it comes to airport operations that have a negative impact on our residents."

This legal stone hurled at Goliath is unlikely to have the same result David did in the Bible. But to paraphrase another biblical passage, perhaps some day the lion and the lamb shall lie down together.

Contact Tom Belden at 215-854-2454 or tbelden@phillynews.com.