The Flying Boats
Pan Am Clipper Flying Boats
Before WW II, international air travel in the flying boats was a huge step in opening up what was possible for flying passengers. (Granted, only for those with a bit of money). Sikorsky S-40, S-42, and VS-44 A as well as the Boeing B-314 opened the era of intercontinental air travel. (Hmm, Martin M-130 China clipper as well).
You can see the VS-44A Excambian in the New England Air Museum in Windsor Locks, CT. The story of how that plane got there (once owned by actress Maureen O'Hara and her husband) and was restored is pretty neat.