Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 175; Flight Crew Total 6720; Flight Crew Type 190
Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Human Factors
Upon arrival into ATL; we received a visual approach clearance after calling the airport 'in-sight'.  We were level at 3000 ft intercepting final approximately 8-9 miles from the runway.  I went heads down to the FMS to extend a centerline off the FAF and we both confirmed.  Meanwhile; the Captain started a descent visually using vertical speed and using outside references.  When I finished with the FMS I noticed we were in a descent around 2100 MSL and that we were low.  I queried the Captain on his altitude; stating we were low.  He corrected by clicking off the autopilot; and began a climb back up to the FAF altitude which was around 2700 ft MSL.  As he began climbing ATC issued and Altitude Alert.  We acknowledged ATC; continued climbing to a safe altitude; and continued safely to the runway.  Since we had visual contact with the airport and all terrain; safety was never compromised.
B737 First Officer as pilot monitoring; reports the Captain descending below the FAF altitude by 700 feet before reaching it on a visual approach. ATC issues a low altitude alert at the same time the First Officer is pointing out the deviation to the Captain.