Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Situational Awareness; Distraction
Deviation - Altitude Overshoot; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Environment - Non Weather Related; Human Factors
Cleared to 'cross ZZZ at or above 14;000 feet; cleared for the ILS Z XX approach.'  Inattention to what mode the descent was in and tied with teaching on an OE; I descended to approximately 13;000 feet before realizing the error. We were in VMC conditions and had terrain in sight.  ATC did not mention the error.Performing OE for new FO and inattention to cleared altitude. Pay more attention during training on OE.
PM on OE and cleared to cross ZZZ at or above 14;000 feet; then cleared for the ILS Z Runway XX approach.  VMC with terrain in sight; descended below 14;000 feet prior to ZZZ.  Noticed the error; but ATC did not say anything.  Continued the approach and landed without further incident. Probably inexperience with the plane mostly; and also recency/currency; this was my first flight in an actual plane in about 7 months.  It was a new plane (I was on OE) and an unfamiliar airport.  The Check Airman and I had discussed the arrival/approach and how he was going to fly it during cruise but at the time were reviewing how to use the different descent modes to fly the approach and were momentarily distracted.More active monitoring and attention to what the plane's programming is doing; also experience in the plane will likely help.
Air Carrier flight crew descended below their cleared altitude. The crew cited distraction and the FO's lack of flying as contributing factors.