B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance; Flight Crew Landed As Precaution; Flight Crew Landed in Emergency Condition; Flight Crew Took Evasive Action; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
At FL390 we got Main Cargo Door warning; pressurization was normal; we followed QRH checklist; we advised ATC and descended to 10;000 feet; notified the company and returned to ZZZ. approach and landing was uneventful.
B767 Check Airman reported getting a Main Cargo Door warning during cruise; resulting in an air turnback.