From the ramp tower 120 feet above the runway, it's clear Philadelphia International Airport is surrounded by water. There is wetland, a network of creeks and, just a couple hundred yards away, the tidal Delaware River leading out to the bay. As with many airports, the original idea was to build on a large tract of land convenient to a city but far enough away from homes and tall buildings. Often, that meant coastal wetlands and landfill.
Now, such airports are threatened.