Border Patrol Agents who work at airports have a bit more responsibility than those who are stationed at other locations. Agents working at airports that are located within 100 miles of the US-Mexico border work closely with the Transportation Security Administration agents at those airports to monitor travelers.
Border patrol agents usually do not have dedicated offices at the airports like other federal agency workers do. They are typically dressed in plain clothes as opposed to wearing the standard-issue BP uniforms and there has never been confirmation from Border Patrol officials regarding how many of its agents are stationed at a given airport at any given time.
There is little doubt, however, that the agents have a presence at those airports as they often stand beside TSA agents and do eyeball checks of green cards, passports, and other forms of ID that travelers show in order to help spot suspicious individuals or activity.
Agents are also looking for behavior that typifies illicit or illegal behavior or intent such as extreme nervousness or the appearance of being lost. If an individual displays this type of behavior but has what appears to be valid identification, the BPO agent will begin asking a series of questions such as how long it’s been since they entered the country and where the individuals mother was born. Agents can often detect lying not so much by the answers to these kinds of questions but rather to the behavior displayed while answering them.
It is easy for laypersons to confuse Customs agents and Border Patrol agents who work at airports. But while both are part of US Customs and Border Protection (CBP), Border Patrol agents are only stationed at airports within 100 miles of the border whereas Customs agents are stationed at all international airports and use an electronic database to make determinations about who is and is not allowed to travel into the US. Border Patrol agents at airports do not use that database.