Seeking information regarding secret missions over Pacific in early 1950s

I'm looking for information about my great-grandfather Loren Lester Green (Sr.) who flew secret missions over the Pacific after the Korean War until his death in 1956. He was a pilot. I don't know much about those missions as my grandmother (his daughter) only recently found out while in China when she happened to meet someone who intercepted radio signals from his plane. I'm not sure where to even begin looking for information about those secret missions. I know Loren ended WWII as a 1st Lieutenant, flew in the Korean War, and died as a Captain in Honolulu, Hawaii. (It would also be nice to learn about his service in the Korean War; I have almost no information about his life other than these brief tidbits. However, my priority right now is information about the secret missions.)