After boarding, they did not take their assigned seats but dispersed to seats in the first row of first class, in the midcabin exit rows and in the rear—the exact configuration of the 9/11 execution teams. The head of the group, seated closest to the cockpit, and two others asked for a seatbelt extension, kept on board for obese people. A heavy metal buckle at the end of a long strap, it can easily be used as a lethal weapon. The three men rolled them up and placed them on the floor under their seats.

Mr. Shahin told television reporters that he needed the seat-belt extension because he weighs 280 pounds. However, the police report lists his weight as 201 pounds. Weights listed for the other imams ranged from 170 pounds to 250 pounds.

And lest this entire incident be written off as simple cultural ignorance, a frightened Arabic-speaking passenger pulled aside a crew member and translated the imams' suspicious conversations, which included angry denunciations of Americans, furious grumblings about U.S. foreign policy, Osama Bin Laden and "killing Saddam."

We have a new, inviolate aviation standard after 9/11, which requires that the captain cannot take that airplane up so long as there are any unresolved issues with respect to the security of his airplane. At altitude, the cockpit door is barred and crews are instructed not to open them no matter what is happening in the cabin behind them. This is an extremely challenging situation for the men and women who fly those planes, one that those who write federal aviation regulations and the people who agitate for more restrictions on a captain's authority will never have to face themselves.

Likewise, flight attendants are confined in the back of the plane with upwards of 200 people; they must be the eyes and ears, not just for the pilot but for us all. They are not combat specialists, however, and to compel them to ignore all but the most unambiguous cases of suspicious behavior is to further enable terrorists who act in ways meant to defy easy categorization. As the American Airlines flight attendants who literally jumped on "shoe bomber" Richard Reid demonstrated, cabin crews are sharply attuned to unusual or abnormal behavior and they must not be second-guessed, or hamstrung by misguided notions of political correctness.

The Air Carrier Security Committee of the Air Line Pilots Association investigated the incident and said, "The crew's actions were strictly in compliance with procedures and demonstrated overall good judgment in the care and concern for their passengers, fellow crew members, and the company."

"The decisions made by all the parties were made as a result of the behavior of the passengers and not as a result of their ethnicity," the report concluded.