A tank on a firefighting aircraft initially is loaded with water. A polymer gel emulsion vessel is provided on the aircraft, but is not activated and mixed with tank water until such polymer gel preparation is initiated by an operator. When initiated, a pump pulls water from the tank and doses it with gel emulsion. Double elbows and/or the pump impeller fully activates the polymer gel. The activated polymer gel is mixed within the tank by one of a variety of systems including mixing paddles or sparging with gas. In one embodiment, a hollow tower of telescoping form has a float to keep an upper end near a surface in the tank and a sparging gas entry is a controlled distance below the surface, such that gas of limited pressure, such as from a ram air inlet can sparge and mix the water and activated polymer gel emulsion effectively.