Kurenai no Buta, Tenkuu no Shiro Laputa Recommendations
They're both directed by Miyazaki and created at Studio Ghibli. They're both adventure films that have air pirates. Also, the two main characters in both are an engineer and a mysterious character somehow affected by magic.
Same director, same time, same animation studio. It should not surprise that both movies are similar. Hayao Miyazaki's love for flying shines through in either case. Especially the scenes among the pirates could be stitched together without a visible seam. The biggest difference comes in the form of the main characters, an older scoundrel in Porco Rosso, a young adventurer in Laputa.