Regional Jet 700 ER/LR (CRJ700)
Flight Crew Commercial
Situational Awareness; Distraction
Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Procedure; Human Factors
Flying at FL240 we were queried by ATC; 'Say assigned altitude.' We glanced at the altitude preselected which indicated FL210. Immediately upon discovering the discrepancy we replied to ATC; 'Leaving FL240 for FL210' and began our descent. As the pilot flying; I could not recollect ever receiving or acknowledging the clearance to FL210. The flight attendants had called up to the cockpit with a question shortly before the incident (which may have been the time the clearance to FL210 was given). To our knowledge; there was never any traffic conflict and the controller said nothing else to us after we initiated our descent.
CRJ-700 flight crew failed to descend until alerted by ATC even though they had 'preselected' the assigned lower altitude.