How does the author use flashback in the novel, Alnilam?

Alnilam abounds in flashbacks and digressions and in rich narrative sequences, such as the recounting of blind curmudgeon Cahill at the controls of an airborne plane or his encounter with Hannah Pelham, who transmits the gonorrhea she acquired from his son Joel. However, during almost seven hundred pages of ornate language and schematic symbolism, the reader's identification with Frank Cahill's befuddlement might extend to his admission that: "He was by now thoroughly tired of talk about flying, of having its special terms explained to him."