Piper's Navajo business twin was introduced in 1967 and manufactured until 1983. Initially it had 310 hp Lycoming TIO-540 engines but the PA-31-325 announced in 1975 has 325 hp L/TIO-540s. Standard cabin layout is for two crew and four passengers with a small restroom in the back but 9-place seating is possible with an optional freight door available.