Chemtrail conspiracy theory
Several photographs on the Internet have been claimed to show the inside of planes that spread chemtrails. They show ballast barrels installed on the inside of the plane. In reality, these are photographs of test planes or firefighting planes. The real purpose of the barrels is to simulate the weight of passengers or cargo. The barrels are filled with water, and the water can be pumped from barrel to barrel to test different weight distributions while the aircraft is in flight.