A cargo airplane is transporting patients from a mental hospital. The patients are going all crazy in the cargo playing a soccer with an invisible ball. The pilot has had enough of it, tells the copilot to guide the plane, and goes in the back to make them stop the noise. They stop, the pilot returns to the cabin, but after 5 minutes, it starts all over again. The pilot asks the co-pilot to give it a shot at calming the patients down. The co-pilot goes in the back, the noise stops, and he returns in the cabin. Half an hour later, the plane is quiet. The pilot is impressed and asks the copilot how he did it. The copilot replies: ""I told them: soccer is not allowed indoors. You have to take it outside.""