Not sure if this is the best place for my question, but here goes.

Between October 2017 and October 2018, my wife and I made three trips to Italy, business class on Swiss from Boston. On the third trip, my wife was selected for additional screening at the gate in Zurich before our flight to Boston. We didn’t think much about it for the next three years. We did not fly again until a return to Italy this past October. No problem flying Boston to Newark to Frankfurt to Venice.

On our return we had no trouble at FCO, flying Swiss to Zurich. However, my wife was again selected for screening in Zurich at the gate for our Swiss Boston flight. Her boarding pass was stamped S S S S. The agent says she was selected by TSA and this will happen every time she flies for 5 years.

An acquaintance of ours is a TSA manager. His pupils dilated a little when we told him about the SSSS on her boarding pass but his jaw dropped when we mentioned that she has a Global Entry card. (In fact, she renewed it successfully without an interview not long after the flight in question.) Trust me, she is not a security risk and has never done anything questionable on a flight. He told us this makes no sense and that TSA could not have tagged her as a risk but then let her continue as a Trusted Traveler.

How do we figure this out? Is the problem with Swiss International or with Zurich airport security? What are we missing? Odd that there were no problems with any of the other flights that trip. We are not flying to Europe again anytime soon but want to know if we will need to steer clear of Switzerland in the future.