A man who plotted to bomb New York City's subways -- and then switched sides and helped the U.S. prosecute terrorists after his arrest -- has been sentenced to 10 years in prison.

A judge called it “a once unthinkable second chance” after sentencing Najibullah Zazi.

Zazi was charged back in 2009 with plotting to bomb New York City's subways.

He had faced the possibility of life in prison, but he's spent the past 10 years cooperating with authorities, providing "extraordinary" assistance to U.S. counterterrorism authorities.

He testified against other al-Qaida members and gave information to U.S. investigators.

Zazi apologized Thursday, saying he was brainwashed.

The naturalized U.S. citizen acknowledged in a 2010 guilty plea that he and two friends planned rush-hour suicide bombings on subway lines around the eighth anniversary of the Sept. 11 terror attacks.
 
The 10-year prison term means Zazi could be released from prison soon. He has been in custody for a decade.

He will have a lifetime of supervised release.