In passing through these checkpoints, each of the hijackers would have been screened by a walk-through metal detector calibrated to detect items with at least the metal content of a .22-caliber handgun. Anyone who might have set off that detector would have been screened with a hand wand-a procedure requiring the screener to identify the metal item or items that caused the alarm. In addition, an X-ray machine would have screened the hijackers' carry-on belongings. The screening was in place to identify and confiscate weapons and other items prohibited from being carried onto a commercial flight.⁷ None of the checkpoint supervisors recalled the hijackers or reported anything suspicious regarding their screening.⁸

While Atta had been selected by CAPPS in Portland, three members of his hijacking team-Suqami, Wail al Shehri, and Waleed al Shehri-were selected in Boston. Their selection affected only the handling of their checked bags, not their screening at the checkpoint. All five men cleared the checkpoint and made their way to the gate for American 11. Atta, Omari, and Suqami took their seats in business class (seats 8D, 8G, and 10B, respectively). The Shehri brothers had adjacent seats in row 2 (Wail in 2A,Waleed in 2B), in the first-class cabin. They boarded American 11 between 7:31 and 7:40. The aircraft pushed back from the gate at 7:40. ⁹

Shehhi and his team, none of whom had been selected by CAPPS, boarded United 175 between 7:23 and 7:28 (Banihammad in 2A, Shehri in 2B, Shehhi in 6C, Hamza al Ghamdi in 9C, and Ahmed al Ghamdi in 9D).Their aircraft pushed back from the gate just before 8:00.¹⁰

Washington Dulles: American 77. 

Hundreds of miles southwest of Boston, at Dulles International Airport in the Virginia suburbs of Washington, D.C., five more men were preparing to take their early morning flight. At 7:15, a pair of them, Khalid al Mihdhar and Majed Moqed, checked in at the American Airlines ticket counter for Flight 77, bound for Los Angeles. Within the next 20 minutes, they would be followed by Hani Hanjour and two brothers, Nawaf al Hazmi and Salem al Hazmi.¹¹

Hani Hanjour, Khalid al Mihdhar, and Majed Moqed were flagged by CAPPS. The Hazmi brothers were also selected for extra scrutiny by the air-line's customer service representative at the check-in counter. He did so because one of the brothers did not have photo identification nor could he understand English, and because the agent found both of the passengers to be suspicious. The only consequence of their selection was that their checked bags were held off the plane until it was confirmed that they had boarded the aircraft.¹²

All five hijackers passed through the Main Terminal's west security screening checkpoint; United Airlines, which was the responsible air carrier, had contracted out the work to Argenbright Security.¹³ The checkpoint featured closed-circuit television that recorded all passengers, including the hijackers, as they were screened. At 7:18, Mihdhar and Moqed entered the security checkpoint.