Travelers passing through major U.S. airports are encountering a more visible presence of immigration enforcement personnel, according to reports from multiple hubs, a shift that has prompted questions from civil liberties groups and the travel industry alike about how the change affects both domestic and international passengers.

The shift marks a departure from the traditionally more limited role immigration agents have played in domestic terminal areas, where enforcement activity has historically focused on international arrivals and customs processing rather than general terminal presence.

Airlines and airport authorities have generally avoided public comment on the specifics of federal enforcement operations within their facilities, deferring questions to federal agencies.