Twenty minutes into a recent LAX JFK flight, the pilot announced the air rafts flaps were not working properly and would return immediately to LAX. It appeared the pilot was using the engines more than the flaps on the descent and we landed using heavy reverse thrust. Fire engines along the runway on landing. We waited for the fire crew to make sure there was nothing wrong with aircraft (wheels primarily) before heading to the gate. The flight purser did most of the communication inbound and after landing. Very adequate, and I really didn't need to know the technical reason for the aircraft difficulty.