During a 30-day test period between February and March, 5,000 American Airlines international passengers missed their connecting flights — in large part because the current immigration and customs setup is so slow, airport officials said, adding that they aim to bring those numbers down.

The secure area, a dense warren of offices, interview cubicles, waiting areas, weapons-storage depots and jail-like holding cells, is where travelers whom agents want to interview will be taken. There also is a secondary interview area divided into three sections separated by locking doors.

A third area has spare cells containing a bench and a metal toilet in which travelers with serious issues, including contraband or phony papers, will be held for transfer to immigration or criminal detention. The cells have padded, reinforced walls and solid metal doors. Viewing windows in the doors have sliding covers that shut with a loud metallic bang.

Manufacturers make quieter covers, but federal agents wanted the noisier, more intimidating type, Abreu said.