Two suspected terrorists have been arrested in Amsterdam by Dutch police at the request of the United States government after their arrival from Chicago on a United Airlines flight.

The pair, Ahmed Mohamed Nasser al Soofi of Detroit, Michigan and Hezem Abdullah Thabi al Murisi were both charged with “preparation of a terrorist attack,” according to U.S. law enforcement officials quoted by ABC News.

Al Soofi began his flight in Birmingham, Alabama, while al Murisi started in Memphis, Tennessee. Although both are Yemeni nationals, both have been living legally in the United States. Each flew separately to Chicago’s O’Hare International Airport, and sent his bags on to Washington D.C.’s Dulles International Airport, to be sent on to a flight to Dubai, and eventually, to Yemen.

However, neither man boarded that flight. Instead, they both changed their flights at O’Hare, and boarded a United Airlines direct flight to Amsterdam, raising suspicion. Federal air marshals were on the United Airlines flight to Amsterdam, according to U.S. law enforcement officials.

What Took So Long?

Security personnel in Birmingham were the first to pick up on the fact that something was wrong.

Despite the sultry August heat in America’s Southland, al Soofi was wearing bulky clothing and carrying $7,000 in cash. He was also carrying in his checked luggage a cell phone taped to a Pepto-Bismol bottle -- a “kind of mock explosive,” the FBI told ABC News – as well as three other cell phones taped together, several watches taped together, a box cutter and three large knives.

However, law enforcement in the United States is a methodical process. It is not illegal to carry knifes or taped cell phones and watches in checked baggage on domestic American flights. Because there were no explosives in the bags, the luggage was cleared for the flight, and al Soofi was allowed to go. 

In Chicago, officials noticed that al Soofi did not board the Dulles-bound flight with his bags, which were headed for Dubai and Yemen. They also noticed he was joined by a second man, al Murisi, and notified officials in Washington.

It was at that point that Customs and Border officials issued an alert, ordering the plane to Dubai to turn around and return to the gate. Al Soofi’s bags were pulled off the flight and searched a second time. Officials said no explosives were found, but once the suspicious items were discovered, Dutch authorities were notified.

 “This was almost certainly a dry run, a test,” a law enforcement official told ABC.