This infrared video, shot from a New South Wales Rural Fire Service aircraft, shows a DC-10 air tanker dropping on a wildfire in Australia. In the normal video the aircraft disappears in the smoke, but after switching to IR it can be seen again. The water or retardant it drops shows up as black, much cooler than the fire which is white.
In addition to the drop, there is fascinating IR footage of thousands of burning embers being blown downwind. A spot fire can be easily seen thanks to the IR soon after it starts. It later grows very large.