Kurenai no Buta, Kaze wo Mita Shounen Recommendations
Similar alternate world time line involving technology and weapons including open cockpit planes. Neither are really "steampunk" but have a bit of that feel about them. Porco Rosso is far more lighthearted than The Boy Who Saw the Wind but still touches on the pain caused by war, Porco more from a veteran's standpoint and TBWStW from that of an child caught up in it. Both can be enjoyed as fun and fanciful but both touch on some deeper stuff if you want to go there. Both are excellent.