John C. O'Connor, 58, a member of the staff of the Johns Hopkins University Applied Physics Laboratory and a former Navy flyer, died of cancer Saturday at his home in Silver Spring.

Cmdr. O'Connor, who was born in Chicago, Ill., graduated from the University of Maryland. During World War II, he was commander of a fighter squadron for the U.S. Navy and served in the Pacific. Cmdr. O'Connor moved to the Washington area in the mid 1950s. He worked at the Bureau of Naval Weapons as a weapons program until 1961, when he retired from the Navy.

Two years retiring from the Navy, he joined the staff of the Applied Physics Laboratory. While employed as a senior staff member there, he worked for the Fleet Systems Department, was involved in defining the antiaircraft defense systems for new ships, and in 1975 participated in the Polaris program. He had been on disability leave at the time of his death.

Survivors include his wife, Mervyn, of the home in Silver Spring; two sons, Thomas, of Chicago, Ill., and Michael, Md.; a stepmother, Gerda O'Connor and stepsister, Susan Hrudka, both a Winnetka, III.; and a stepbrother, the Rev. Francis Duncan, of St. Ambrose College in Davenport Iowa.