Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 137; Flight Crew Total 4072; Flight Crew Type 1818
Confusion; Fatigue
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors
Flight was air return due to airborne mechanical event. Upon taxi out; second time around; we were all tired from the air return plus being into our Window of Circadian Low (WOCL) on taxi out. ATC cleared us to taxi to 22L via RF; ALPHA and SIERRA. We instead went RF BRAVO and ROMEO. FO was heads down with new checklist and IRO was helping. About half way to the runway; FO realized we were in the wrong spot and asked ATC for a revised clearance; which they were fine with since we were the only airplane operating on the field at that hour.
B757 Captain reported a taxiway incursion during taxi out due to fatigue; after a maintenance delay.