WASHINGTON -- U.S. law enforcement was already on the lookout for possible hijackers when two Yemeni men ran what's being called a dry run of a terror attack.  ABC News reports that federal air marshals were aboard the flight from Chicago to Amsterdam and were keeping a close eye on the men.  Dutch police arrested Detroit residents 48-year-old Ahmed Mohamed Nasser al-Soofi and 37-year-old Hezem Abullah Thabi al-Murisi Monday.

The men had checked bags in Chicago through to Dubai before boarding a completely different flight.  U.S. officials let them travel for what they called "investigative purposes."  Al-Soofi had triggered a security alert after his luggage contained what law enforcement called mock bombs.  The items included a cell phone taped to a Pepto-Bismol bottle, three cell phones taped together, several watches attached to one another with tape and seven-thousand dollars in cash.  Authorities also found a box cutter and three large knives in their bags.