In gratitude for the loyalty of their favorite teacher Justus, who teaches them the value of friendship and solidarity, the pupils of the Bamberg boys' boarding school want to reconcile him with his old friend Robert Uthofft, known as "Non-Smoker". The former doctor, who lives in the non-smoking compartment of a disused train carriage, always makes time for the boys and offers them advice and support. One day, Johnny's classmate Uli desperately decides to test his courage after being teased numerous times: he jumps out of the window on the top floor of the school using an umbrella as a parachute. When the non-smoker saves the seriously injured Uli in a spontaneous emergency operation, he not only gets closer to his old friend Justus again, but also to the sympathetic school nurse Beate. Then the class is about to perform their play "The Flying Classroom", in which the class can fly to any part of the world in an airplane they have built themselves. The pupils have no idea that the dream of flying could soon come true for all of them.