Martin (Marty) Knutson, who flew U-2 spy planes over the Soviet Union during the Cold War and later led NASA’s program of high-altitude research with the same aircraft, died Dec. 11 in Los Altos Hills, Calif. He was 83.

Knutson was born and raised in St. Louis Park, and attended the University of Minnesota, but left in 1950 before graduating. He joined the U.S. Navy, then transferred into the newly created U.S. Air Force, where he learned to fly fighter jets.

After serving in the Korean War, he was among six elite pilots chosen by the CIA Air Division to fly lengthy missions deep inside the Soviet Union to photograph military and missile sites at 70,000 feet. He eventually served at bases in Turkey, Germany and England.

When Knutson first saw a U-2, he noticed it didn’t have a control stick. It had a yoke — more like a steering wheel — and he almost walked away.

“Either you flew with a stick like a self-respecting fighter jock or you were a crappy bomber driver,” Knutson told author Giles Whittell for his 2010 book, “Bridge of Spies: A True Story of the Cold War.”

Knutson flew two secret Soviet overflights in 1956 and 1959. The latter flight lasted more than nine hours, and Knutson landed with just 20 gallons of fuel remaining, according to a declassified NASA history. Knutson’s surveillance work helped reveal that the Soviets didn’t have as many long-range bombers as they let on, tamping down U.S. fears of a bomber gap.

His second and last reported Soviet overflight was just 10 months before U-2 pilot Francis Gary Powers was shot down in Soviet airspace and captured — an incident that set back U.S.-Soviet relations. Knutson knew and respected Powers. “His deportment through the whole affair … made me think, ‘I am proud to know that guy,’ ” Knutson later told a newspaper reporter.

Knutson eventually settled in California with his wife, Jeanine, and family, and returned to Minnesota frequently. His children said his Minnesota roots were apparent in his love of fishing and hunting. He also played golf and in the 1990s took up scuba diving.

“He never let us cheer any other team but the Vikings, no matter how good or bad they did,” said his son, Eric, who is a program manager in Lockheed Martin’s skunk works, where the U-2 and other advanced aircraft have been developed.

After leaving the CIA, Knutson joined NASA in 1971 to manage U-2 flight operations at its Ames Research Center in Moffett Field, Calif. He flew earth-science missions on projects to study the stratosphere and produce aerial maps.

In 1984, Knutson was promoted to flight operations director at Ames as well as site manager of NASA’s Dryden Flight Research Facility at Edwards, Calif., where space shuttle landings took place. NASA, in a biography posted on its website, said he was a leader on numerous research projects. He also test-piloted experimental aircraft, his daughter Kristin said.

In 1990, as the Air Force considered eliminating another reconnaissance aircraft, the SR-71 Blackbird, Knutson led the successful effort to have three of them transferred to NASA. Knutson spent his last seven years with NASA at Ames and retired in 1997.

He is survived by a sister, Donna Edwards, Orono; four children, Martin Knutson, Eric Knutson and Robin Knutson Replogle in California and Kristin Knutson in Oregon, and five grandchildren.

A memorial service is at 1 p.m. Jan. 25 at the former Moffett Naval Air Station Officers Club at NASA Ames Research Center, Mountain View, Calif.