Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 75
Fatigue; Distraction; Human-Machine Interface
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Environment - Non Weather Related; Human Factors
Before the TOD; we briefed the arrival and programmed the FMC to descend via the ZZZZZ RNAV STAR correctly. When we got clearance from ATC to descend via the STAR; I selected 4;000 feet in the MCP window as previously briefed. Somewhere below 10;000 feet; ATC gave us vectors off the STAR and to descend and maintain 5;000 feet. We complied. I selected 5;000 feet in MCP window; HDG Select and LVL Change and informed the PM. Sometime later ATC gave us direct to ZZZZZ fix and descend via STAR. I programmed direct to ZZZZZ in the FMC; selected LNAV and set 4;000 feet in the MCP window as per the STAR. I informed the PM.We had a frequency change and the PM got a new ATIS at the same time as that was taking place.  As we are approaching ZZZZZ fix; ATC confirmed that we were descending to 4;000 feet instead of crossing ZZZZZ fix at 5;000 feet.  That's when I realized that we were in LVL Change pitch and not in VNAV. As I was communicating that to the PM; ATC gave us a further descend and vectors for the final approach.  The rest of the flight was uneventful. There were no TCAS TA or RA at any time. We debriefed the incident at the gate. I realized that due to recent events regarding the future of my flying career and the constant uncertainty has hindered my rest. This may have been a factor for my distraction on missing such a small yet critical step.
Air carrier Captain reported not descending via the STAR due to selecting LVL Change Pitch instead of VNAV on the MCP.