Miller on the terror plot that almost happened

(CBS News) It is being called the most significant terror plot on U.S. soil since 9/11.

On Monday a prosecutor told jurors that in September 2009, three men were just days away from carrying out suicide attacks in New York City's subways.

Najibullah Zazi and Zarein Ahmedzay said in their guilty pleas that they wanted to avenge U.S. aggression in the Arab world. Both will testify for the government against a third man, Adis Medunjanin, whose trial began Monday in New York. Medunjanin is an accused al Qaeda operative who allegedly discussed bombing New York City movie theaters, Grand Central Terminal, Times Square and the New York Stock Exchange before settling on the city's subway system.

Senior correspondent John Miller called it "the plot that almost happened."

Prosecutors: Foiled terrorist pondered other NYC targets

"We talk about these plots all the time," Miller said on "CBS This Morning." "Usually they're undercover sting operations: the FBI has all the controlling features, they make the bombs, they record the meetings. In this case they literally found out 24 hours basically beforehand, as Najibullah Zazi (who will be a witness in this case), got in his car with explosive components and headed for New York for targets in the New York City subway system."

Miller, who was working in the FBI at the time, said Zazi, a shuttle bus driver at Denver International Airport, was known to be in contact with al Qaeda, and his movements were being followed minute-by-minute.

"When he rented that car to drive to New York and then booked a flight back, the first thing we said was, 'What does he have in that car that he is bringing to New York that he can't put on a plane to get there?'" Surveillance teams followed Zazi from Denver to New York, where was arrested.

"What's interesting about this is we have all wondered since 9/11 why there have not been second or third attacks, especially in subways and places like this," said Charlie Rose. "The answer is, they have been tried but thwarted."

"That's right," Miller said. "And this would have been that."