Answer
The plastic explosive used by Umar Farouk Abdulmutallab was PETN, a powerful and unstable material often employed in military and terrorist operations due to its sensitivity to shock and heat. Abdulmutallab concealed it in his underwear in an attempt to detonate it on a transatlantic flight on Christmas Day in 2009, fortunately, the device malfunctioned and failed to explode, resulting in his arrest and subsequent conviction.