Sewn into the underwear of Umar Farouk Abdulmutallab was a powerful plastic explosive, the authorities say.

Had Mr. Abdulmutallab, sitting in seat 19A of Northwest Airlines Flight 253 on Friday from Amsterdam to Detroit, been able to set off the explosive, it might have blown a hole in the side of the airplane and caused it to crash, experts believe.

Mr. Abdulmutallab, 23, a Nigerian citizen, was charged in a federal criminal complaint on Saturday with the willful attempt to destroy an aircraft with an explosive device.

The complaint identified the explosive as pentaerythritol tetranitrate, or PETN.

Introduced after World War I, PETN is in the same chemical family as nitroglycerin and among the most powerful of explosives. It was the same explosive that Richard C. Reid tried to detonate in his shoes during an American Airlines flight in December 2001.