John Murray Rowe Jr., a 67-year-old former defense contractor from South Dakota, was sentenced to over 10 years in prison for attempting to share classified U.S. Air Force information with Russia, the Justice Department said Monday.

Rowe, who held top security clearances during his nearly 40-year career, pleaded guilty to espionage charges after communicating extensively with an undercover FBI agent he believed worked for Moscow.

Prosecutors said he provided details on U.S. fighter jet countermeasure systems and expressed willingness to work for Russia if he couldn’t find employment in the U.S., CBS News has reported.

He was also fined $25,000 and will serve three years of supervised release after prison.