Date: 201908
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Aircraft: B767-300 and 300 ER
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Fatigue; Situational Awareness; Workload
Anomaly: Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Arrival clearance into ZZZ was ZZZZZ to join LOC Runway XX. STAR and approach were briefed appropriately during cruise flight. Passing ZZZZZ1; and approximately 2;500 ft. MSL; we were directed to switch to Tower; we checked in and received clearance to land. At approximately 2;200 ft. MSL; PF (Pilot Flying) dialed altitude window to 100 ft. above touchdown zone. Passing final approach fix; PM (Pilot Monitoring) reminded PF that the aircraft needed to be stable no later than 1;000 ft. AGL. Focus of both PF and PM became configuring the aircraft and VNAV was not selected at Final approach fix. At approximately 1;400 ft. MSL; the aircraft entered VMC; and both PF and PM saw 'field in sight'. We also immediately realized that we were low; seeing '4 red' on the PAPI. The PM announced 'yours look low;' the PM verbally agreed; disconnected the AP (Auto Pilot) and AT (Auto Throttle); and while remaining VMC; initiated a climb until appropriate PAPI glideslope of 2 red and 2 white was achieved. The visual glideslope was verified by the PM by double checking that the 3.5 degree glideslope shown in the HUD was in the landing zone and abeam the PAPI. At no time were we unstable during this approach. After the AP was disconnected and a climb was established; ZZZ Tower issued a verbal low altitude warning; which was acknowledged by the PM. There was no further communication with ZZZ Tower until after landing. That communication was to 'join Bravo; B4; cleared to cross Runway XX; Foxtrot to the ramp.' No comment was made by the flight crew or the Tower about the low altitude call; and no other communications were made between the aircraft and the Tower/Ground (all one frequency at that time of day).Fatigue was a factor. The crew was focused on configuring the aircraft and did not insure that proper vertical navigational guidance was engaged crossing the FAF (Final Approach Fix).[My] suggestion [is] better sleep prior during the trip sequence. Both the Captain and the FO (First Officer) had discussed how tired we were during the previous ride to the ZZZ1 ramp earlier that night and also during the enroute portion of the flight - knowing that; we should have verbalized that same opinion before the top of descent. This would have led to a heightened awareness that we were not at our peak performance. [Also;] greater attention to detail during the approach.




Synopsis: Boeing 767 Captain reported low altitude on approach due to fatigue.