At the airport in Lisbon the officer stamped my passport and, handing it back, said, “Have a nice flight.” Moments later, waiting to board, I was pulled out of the line and taken to the side for a pat-down and a search of my luggage. After the man had completed the procedure, I asked him why I had been singled out. He pointed to the four letters at the bottom of my boarding pass and then gave me something I’ve never received from TSA: an apologetic shrug.