Passengers selected for the additional screening are separated from the line and may be subjected to enhanced security procedures including, checking and matching passenger identification and boarding passes, conducting physical searches of carry-on luggage and using handheld explosive detection units. The behavioral screening checks are unannounced and may be done at any gate, at any time.
While the TSA acknowledges that displaying stress or fear while waiting in line to get on an airplane does not automatically mark a person as a terrorist or criminal, they believe the enhanced behavioral screening can help their security officers determine if an individual poses a higher security risk.
"Passenger safety continues to be our mission as we use flexible measures in our approach to random screening" assures the TSA in a press release. "Your safety is our priority." So, whatever you do, relax.