To catch our flight in Philadelphia, we took Amtrak to the 30th Street Station and transferred to a subway to the airport — a viable option if you're not carrying an excess of luggage. The subway cost? A most reasonable $7 per person.
One oddity of our travel experience is that of all the transportation centers we passed through — including airports in Philly, Lisbon, Madrid and Palermo — by far the most visible and heavily armed security was at the 30th Street Station. Either security officials received specific, credible evidence of an imminent threat or there has been a serious misallocation of counterterrorism resources in the United States.