In an alternate history set in the Adriatic Sea during the interwar period, the film follows Marco Pagot, a World War I fighter pilot who has mysteriously turned into an anthropomorphic pig. Known as "Porco Rosso," Marco now spends his days as a bounty hunter, chasing air pirates who wreak havoc on seaplanes and shipping routes. With his signature red plane, he battles pirates led by the Mamma Aiuto gang, creating a reputation as a skilled and fearless aviator. Despite his heroics in the sky, Marco grapples with a complex emotional life, illustrated by his relationships with Gina, a singer and bar owner, and Fio, a young and talented mechanic who dreams of becoming an aviation engineer.

Marco frequently visits Gina's hotel, enjoying her company while reflecting on his past and his curse. Things take a turn when an ambitious American pilot named Donald Curtis arrives, seeking both fame and Gina's affection. Curtis challenges Marco to a duel in the sky, setting the stage for a thrilling air battle. As the rivalry intensifies and danger escalates, Marco is forced to confront not only Curtis but also his own inner demons and the haunting memories of war. The high-flying adventure teems with themes of love, redemption, and the exploration of human nature under extraordinary circumstances, leaving the resolution up in the air as tensions rise.