Reinert began his career as a journalist with the Houston Chronicle in the mid-1970s before moving to freelance work. His articles appeared in several publications, notably Texas Monthly. By the late 70s, he was working as an apprentice to screenwriter-director Robert Benton and subsequently worked on productions of music videos. In 1990, he produced and directed the documentary, "For All Mankind", about the NASA space program which earned him an Oscar nomination. Five years later, he put that knowledge to work as co-scenarist of Ron Howard's "Apollo 13" (1995), adapted from astronaut Jim Lovell's memoir about the failed 1970 space mission. He and co-scripter William Broyles Jr. earned an Oscar nomination.