B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 152; Flight Crew Total 4914; Flight Crew Type 4914
Communication Breakdown; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Flight Crew Became Reoriented
Airport; Environment - Non Weather Related; Human Factors
On approach to 35R; we were direct FRONZ; cleared visual approach. We were on an angled intercept to final. Captain asked 7;000 ft. be set for FRONZ; I did and after leaving 8;000 ft.; tower advised our callsign and low altitude alert. I replied to ATC that we were ok; meaning level and clear of terrain at 7;000 ft. We intercepted the glide path to a normal approach and landing. During the low altitude alert we had finished slowing from 190 to 170 knots assigned. Several runway changes and speed changes preceded this event. I believe the Captain was trying to have the airplane; on the assigned speed; desired configuration and omitted the class B floor as I did.
B737 flight crew reported low altitude alert from ATC on approach.