The FBI detonated a bomb in Pennsylvania made of the components Faisal Shahzad intended to use before he resorted to cheaper alternatives. In May, Shahzad left his SUV in the middle of Times Square, where it merely smoked instead of exploding:

Had he built the Times Square device the way he had originally intended to, terrorist Faisal Shahzad, would have turned his SUV and nearby vehicles into a fatal spray of razor-sharp fragments and transformed building windows into glass guillotines hurtling to the streets, cutting down hundreds of people walking by.

More from AP:

A source close to law enforcement said "too many variables" make a precise damage estimate difficult to calculate adding that the bomb would "have caused a lot of damage." Although surrounding office buildings were mostly vacant on the Saturday evening of the planned attack, the high number of tourists on the street would have contributed to the number of causalities. Two law enforcement officials told The Associated Press that the test explosion destroyed the SUV carrying the properly constructed bomb, damaged other nearby vehicles and scattered flaming debris. The test was conducted in rural Pennsylvania last month.

More from THE WEEKLY STANDARD writers on the Times Square bombing.