The plan was approved by the Federal Aviation Administration in 2010 and supporters say it will bring increased air traffic capacity and make the airport more competitive.

But US Airways believes development of the master plan will come with a much higher price tag, and it is that cost and not merger speculation that has the airline evaluating the future of its hub in Philadelphia.

"We are concerned that escalating costs at the airport will potentially damage the future viability of our hub operation there," US Airways spokeswoman Liz Landau told CNN.

"Any growth at the airport needs to be implemented in such a way that maximizes airport efficiency and makes financial sense for US Airways," Landau said.

US Airways, she said, has a strong record of supporting local and minority owned businesses, adding the carrier would "welcome their continued inclusion in the bid process for any proposed future projects."