As for Philadelphia, it succeeds because robust domestic feed enables a major trans-Atlantic operation. American's JFK hub relies primarily on local traffic between New York and international markets, principally London Heathrow. Philadelphia will likely grow following the merger because it will draw international passengers from a far larger network.
In a prepared statement following the release of the GAO report, US Airways reiterated that Charlotte will remain a major hub. "Charlotte is a key part of the new American Airlines," US Airways said. "With increased connectivity, Charlotte will be a key hub in the combined airline's global network.
"We remain committed to maintaining the current nine hubs of both American and US Airways," the carrier reiterated. "Importantly, our combined network will offer more origins and destinations through each hub, resulting in more travel options for customers and benefits for communities."