Terminal and control tower at Philadelphia airport

PHILADELPHIA, PENNSYLVANIA, UNITED STATES - 2014/01/07: Terminal and control tower at Philadelphia airport. (Photo by John Greim/LightRocket via Getty Images)

PHILADELPHIA, PENNSYLVANIA, UNITED STATES – 2014/01/07: Terminal and control tower at Philadelphia airport. (Photo by John Greim/LightRocket via Getty Images)

PHILADELPHIA, PENNSYLVANIA, UNITED STATES – 2014/01/07: Terminal and control tower at Philadelphia airport. (Photo by John Greim/LightRocket via Getty Images)