Every day, 3 million airline passengers travel into the United States— and every one of them is screened and their baggage checked by one of the 40,000 officers who work on America’s front line. This series documents the challenges faced by CBP at four of the busiest airports in the US including Atlanta, Honolulu, Detroit, San Francisco and Newark. From career drug smugglers and human traffickers to less serious visa and passport defaulters, everyone who comes into the United States by air is subject to scrutiny.