The next time you pass through an airport and have to produce a photo ID to establish who you are and then must remove your shoes, take off your belt, empty your pockets, prove your laptop is not an explosive device and send your briefcase or purse through a machine to determine whether it holds weapons, think about this: In a single day, more than 4,000 illegal aliens will walk across the busiest unlawful gateway into the U.S., the 375-mile border between Arizona and Mexico. No searches for weapons. No shoe removal. No photo-ID checks. Before long, many will obtain phony identification papers, including bogus Social Security numbers, to conceal their true identities and mask their unlawful presence. The influx is so great, the invaders seemingly trip over one another as they walk through the old copper-mining town turned artist colony of Bisbee , five miles from the border. Having eluded the U.S. border patrol, they arrive in small groups of three or four, larger contingents of more than a dozen and sometimes packs of a hundred. Worried citizens who spot them keep the Bisbee police officers and Cochise County sheriff’s deputies busy tracking down all the trespassing aliens. At night as many as 100 will take over a vacant house. Some crowd into motel rooms, even storage-compartment rental units. During the day, they congregate on school playgrounds, roam through backyards and pass in and out of apartment buildings. Some assemble at the Burger King, waiting for their assigned drivers to appear. Sometimes stolen cars are waiting for them, keys on the floor. But most continue walking to designated pickup points beyond Bisbee, where they will ride in thousands of stolen vehicles, often with the seats ripped out to accommodate more human cargo, on the next leg of their journey to big cities and small towns from California to North Carolina. The U.S.’s borders, rather than becoming more secure since 9/11, have grown even more porous. And the trend has accelerated in the past year. It’s fair to estimate, based on a TIME investigation, that the number of illegal aliens flooding into the U.S. this year will total 3 million–enough to fill 22,000 Boeing 737-700 airliners, or 60 flights every day for a year. It will be the largest wave since 2001 and roughly triple the number of immigrants who will come to the U.S. by legal means.