Abstract: A powder and water mixing system which is operatively mounted onboard an aircraft and uses water scooping to automatically produce onboard mixing of powder and water. This system is particularly adapted to drop a fire retardant powder and water mixture from a flying aircraft and includes a pair of tanks, powder containers fore and aft of the tanks, water scoops projecting from the bottom of the aircraft, a pair of powder injection and powder and water mixing devices connected each to a tank, to a water scoop, and to a group of powder containers, a powder container selection valve interposed between each injection and mixing device and the corresponding group of powder containers, and a control connected to each selection valve and arranged to empty a powder container forward of the tanks concurrently with a powder container aft of the tanks, sequentially with water scooping passes by the aircraft.