Originally planned as a comical in-flight short film. Due to the beginning of the Yugoslav Wars, Studio Ghibli developed the film into a feature length movie with a serious tone, while retaining the humor of the manga it was based on.
The flying boats in Porco's World War I flashback story, are based on historical airplanes. Porco and his squadron are flying the Macchi M.5, an Italian single-seat fighter flying boat designed and built by Macchi-Nieuport at Varese. It was extremely maneuverable and agile, and matched the land-based aircraft it had to fight. The Austro-Hungarians are flying the Hansa-Brandenburg CC, a single-seat wooden-hulled fighter flying-boat, named CC after Camillo Castiglioni, financial controller of the Brandenburg company.
The song that Marco (Porco) is listening to on the radio in the beginning is "Le Temps des cerises" ("Sakuranbo no Minoru Koro" in the original soundtrack), which is the song Gina will sing in a later scene.
Porco Rosso's plane engine has the brand Ghibli stamped, and although there isn't such an engine, the animation studio's name was taken from an Italian airplane, the Caproni Ca.309 Ghibli, which had double Alfa-Romeo engines.
Marco Pagot, aka Porco Rosso, was possibly based on Ensign Charles Hammann, a US Navy fighter pilot during WWI. Hammann, like Porco, flew a Macchi M.5 biplane fighter over the Adriatic Sea against Austro-Hungary. He was awarded the Medal of Honor for rescuing, under fire, a fellow pilot who was shot down.
The story is set in the Adriatic Sea east coast between Dalmatian and Kvarner islands,Croatia and a fictionalized city of Fiume after its annexation to fascist Italy and Northern Italy. The concealed beach Porco uses as a hideout bears a strong resemblance to Stiniva, an inlet on the southern side of the Croatian island of Vis.
Sections of the trailer and movie were screened for a multi-celebrity audience at the "Save the Rose Theatre" event. Also see Saving the Rose Theatre (1989). Location of Shakespeare's theatre on the Southbank of London, was approved for museum status granted late in 1998.
Most of the story, except when Porco went to Milan, took place in the Adriatic Sea, between Italy and Croatia.Porco lived on an island on the Croatian shoreline (Vis,Stiniva)of the Adriatic Sea. At first, Miyazaki planned to set the story in Dubrovnik, Croatia.