This paper presents the performance test results of a fault-tolerant inertial reference system featuring skewed axis inertial sensors, sensor redundancy management scheme, and fault-tolerant electronics. This system, built by Honeywell Commercial Flight Systems Group, was calibrated and tested in the laboratory by Honeywell Systems and Research Center. This system was flight tested in 1989, by Boeing Commercial Airplane Company, with excellent navigation and failure detection and isolation performance.A brief description of the system is presented in the paper with emphasis on the fault-tolerant aspects. The performance test results presented include nominal navigation performance and navigation performance under sensor failures. Performance of the failure detection and isolation scheme is also presented.