People have been flocking to a TSA PreCheck RV that is moving around the Denver area, sparking the addition of two more stops before it heads out of town. The program was already extended past its planned four weeks in December because of demand, spokesman Charlie Carroll said last month. Program organizers weren’t too surprised, though, as the Denver International Airport enrollment center has the highest volume of requests in the United States. The RVs can register two people at a time with a maximum of 100 per day, Carroll said.