This paper discusses the integration of a Microwave Landing System and an Inertial Navigation System. The system is built by Lear Siegler, Inc. (LSI) for pallet installation on the USAF C-141 transport aircraft. The main emphasis of this paper is the MLS/INS integration using a constant gain filter algorithm. The system was simulated in the lab, bench tested, and later flight tested on the C-141 using the MLS facilities at Wallops Island, VA. This work was completed for the USAF/ASD under Contract F33615-85-C-3603.