Date: 202103
Local time of day: 0601-1200
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Communication Breakdown; Situational Awareness; Workload; Training / Qualification
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: This was the first leg of a 3-day trip and my 2nd trip in several months. I had not flown in several months due to COVID scheduling (but I have remained current with a PC simulator).  I was having difficulty in clearly hearing ATC and through the interphone in flight.  I was the pilot flying at the time of the event.  My First Officer has been enduring a highly antagonistic situation in the home life; which may have found its way to the flight deck; creating an unanticipated stressor.  My First Officer was distressed over these interactions; resulting in a secondary distraction.On approach; my First Officer (the pilot not flying) believed we were issued a clearance down to 2;400 feet and read back the misunderstood altitude of 2;400 feet.  I did not catch the altitude clearance.  Descending below 3;400 feet; ATC advised us of a low Altitude Alert and informed us that we were meant to be at 3;400 feet.  We apologized and explained it was a misheard clearance.  ATC asked us to climb back up to 3;400 feet and advised us we were still cleared for the approach.  We complied and continued without incident.We discussed as a crew the intention to submit a report that evening.  Being a bit rusty on operating in the physical environment and with the remainder of a 3-day to focus on (including a line check); I inadvertently forgot to write the report.  After our first 2 legs; I was scheduled to split from my First Officer to fly with a line check pilot (per my request prior to the trip) out of an abundance of caution; due to being out of the physical environment for so long.  It may be because we were no longer operating together that my First Officer and I forgot to submit our reports in a timely fashion (without having each other as a reminder).My job as a Captain is to ensure the aircraft is flown in a safe manner and that we comply with ATC instructions. The responsibility comes down to me to maintain total situational awareness in all phases of flight.  I became inadvertently disconnected from the communications loop as pilot flying.  This resulted in a breakdown of a good multi-crew concept; as well as an unsafe situation and unintentional deviation from ATC instruction.  I must remain more diligent and vigilant as a crew member in all aspects of flight; regardless of assigned duty in order to maintain safe and compliant operation.It is also imperative that I participate in SMS in a timely manner; consistent with company standards.  To be an effective team leader; it is also my duty to ensure my crew members take part in SMS.  This can only enhance safety for our colleagues and industry as a whole.  It was never my intention to neglect to submit a report; but unfortunately it was mistakenly forgotten.  I should make reminders for myself to stay on task with necessary reports.  In the future I may find it helpful to set reminders in my phone whenever issues like this arise.


Second narrative: On approach to land; as the First Officer and PM for the leg; I responded to ATC's instruction to descend to 2;400 feet.  My Captain did verify with me the altitude to descend too; since Captain had not heard it clearly.  I advised that the assigned altitude was 2;400 feet.  It wasn't until we were descending below 3;400 feet that ATC checked in and advised that we were to level off at 3;400 feet.  We did proceed to climb back to 3;400 feet and continued the approach to land.The altitude of 2;400 feet was above the FAF altitude and ATC did not correct me when I replied to ATC with the confirmation to descend to 2;400 feet. It was then that; with the 2;400 foot altitude assignment being a bit lower than expected; even though ATC had not corrected me when I responded with a 2;400 foot altitude assignment; I should have verified the altitude assignment.In the future; as a First Officer and soon to be Captain; I will be more vigilant with all procedures and in the interest of safety and full compliance; verify that all direction and communications are clear; concise and without question.  If this is ever in doubt; I will take full responsibility and take all steps necessary to ensure a safe and compliant flight.


Synopsis: Air Carrier flight crew reported an altitude deviation due to a misunderstanding of ATC instructions. The crew cited lack of flying as a contributing factor.