B737-800
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Fatigue; Distraction; Human-Machine Interface
ATC Issue All Types; Aircraft Equipment Problem Critical; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
Air Traffic Control Provided Assistance; Air Traffic Control Separated Traffic; Flight Crew Overcame Equipment Problem; Flight Crew Landed As Precaution; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Software and Automation; Procedure
At XA:55Z the master caution light; auto pilot disconnect aural  warning and IRS annunciation light activated. The FO was the PF and immediately began to hand fly the aircraft. As PM; I verified the aircraft was stable and performed QRH XX.X IRS fault. After completing the required items and discussing all of the impact items; I sent ATC a CPDLC message as to our loss of navigation equipment and inability to remain in RVSM airspace due to the loss of the auto pilot. ATC instructed to remain at FL370 due to traffic. We called dispatch via SATCOM and relayed our current situation and reiterated our need to use the ILS RWY XX into ZZZ due to the loss of RNAV capabilities. After a conference call with Operations and Maintenance; we continued to ZZZ and landed uneventfully via the ILS RWY XX.We split the flying duties to avoid fatigue (30 minute intervals). ATC was given 2 hours to plan our arrival to the opposite runway; and they did an exemplary job. ZZZ1 was built in route 2 as our primary divert airport.
Captain reported total loss of the autoflight systems required close coordination with ATC for traffic separation and special flight handling due to loss of RVSM and RNAV capabilities.