Some colleges have longer plans of study. My school (Georgia Institute of Technology) was ~120 semester-based credit hours, and if you took 17-18 credit hours a semester you could graduate in 4 years. After freshman or sophomore year you really didn't take more than 13-16, which automatically puts you on a 5 year plan. That's also assuming you didn't fail any courses, which was extremely possible in some programs of study. Aerospace Engineering was a 5-6 year major for most, and it wasn't uncommon to see 7th year Aerospace majors.