Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Situational Awareness; Training / Qualification; Troubleshooting
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
Aircraft Automation Overrode Flight Crew
Human Factors; Environment - Non Weather Related
While on final approach the PF was having difficulty slowing the aircraft and continuing the descent. The headwind we had been fighting quickly turned to a crosswind. The PF elected to re-bug and use flaps 40 well above 1;000 feet. As the PF I selected the new flap setting in the FMC and verbally called out the Vref and target speeds. As we were slowing past our previous target speed the PF called for flaps 40. We had no amber band visible for flaps 40 placard speed; so I verified the placard; 162 knots; and selected the flaps seeing 158 knots and slowing on my tape. As I verified the speed brake was armed he again called for 40. The flaps were still at 30. At this point we were now below 1;000 feet but above 500 feet. We discussed the non-movement and load alleviation. As the PM; I suggested; pitch up and slow; the flaps moved to 40 as we suspected they would. The checklist was completed and we were able to be stable by 500 feet AGL; so we continued the landing. We did not observe any limitations being exceeded on the flaps or in procedure as the PM was able to manage the approach prior to the 500 foot gate.In discussing this event during our debrief we believe that we did meet our approach gate criteria. We were in our first 'heavy' approach in many months as the flight was full. The weight may have contributed. The wind was also a contributing factor as it shifted down the final enough that by the time we departed the traffic flow had reversed.Neither of us were averse to going around but it did not seem necessary in the moment as it seemed we met our criteria to continue. Having said that I'm certain eyes further from the instrument panel may have captured data we missed but I believe we trapped and corrected the situation.
While on final approach I; PF; called for final landing flap (flaps 40) and flaps did not move to commanded position (they were at 30); despite being slower than max speed for flaps 40. Since we were within a few knots of max flaps 40 speed; I slowed further and flaps extended to commanded position. I believe the flap extension occurred right around 500 feet.  The final approach speed was within stabilized approach criteria and the outcome of the approach and landing were not in doubt. Landing was uneventful.We have been flying mostly empty airplanes for almost a year and this flight was almost completely full. I believe the higher landing weight coupled with a significant loss of headwind on final contributed to the airplane taking a while to slow down to an acceptable speed for final flaps. When I called for final flaps; we were 3-4 knots below the max flaps speed and I believe the aircraft's safety system was restricting flap movement until I was a little slower. As we return to Pre-COVID passenger loads; I will have to adjust lead time for decelerating the jet. Today was a good reminder.
Air Carrier flight crew reported the aircraft was carrying a pre-COVID passenger load and they were not prepared for the higher flap speeds required for a stable approach.