1x04 Phantom Traveler

The brothers are asked by a man whom Dean and his father had previously rescued to investigate the mysterious crash of a commercial airplane that left only seven survivors, with signs pointing to a demonically-possessed passenger causing the accident. When they realize that the demon is now eliminating the survivors one by one, Dean is forced to face his fear of flying by following its next target (Jaime Ray Newman) aboard an airliner. He and Sam manage to get the demon into a restroom on-board, but it flees its host during the exorcism. Despite this, they continue the ritual, sending the demon back to Hell.