Float Plane: A type of seaplane that has (usually two) buoyant floats to allow for take-off from and landing (alighting, if you insist) on a body of water. Believe it or not, the first racing planes were on floats. There were no long runways back in the day, so starting in 1913 the Schneiders Trophy planes were flown from the water. One notable example was the Supermarine S.6B, a record-setting 400mph float plane that won in 1931. It was a forerunner of the famous Supermarine Spitfire. Floatplane floats are not crude pontoons, but are shaped like a boat hull on the bottom so that they can plane on the surface of the water as the airplane approaches flying speed. In some cases, floats are integral to the design of the airplane, but are nowadays more often in the form of a kit used to modify a suitable land-plane. Amphibious designs incorporating retractable wheels into the floats are possible, but the weight penalty is severe. I flew float planes for years, and in my part of Canada, bush planes are a common sight.
Tech Level: A reciprocating engine (or turbine) is a must, so Dieselpunk.
Appeared In: A friend has written a lovely dieselpunk example, but I cannot share it with you because A) it would be a spoiler, and B) the book isn’t out yet.
For Your Plot: Take your hero off the beaten track. Avoid airports altogether. Flee the zombie hordes.
Flying Boat: The other kind of seaplane. A flying boat is an airplane with a hull designed to act as a watercraft, and propeller placement chosen to avoid spray. Amphibious variations suffer less of a weight penalty than the float planes. The golden age of flying boats may have been the years between WWI & WWII. This was the era of the Pan-Am Clippers, large flying boats that took wealthy passengers across the Atlantic and, in stages, the Pacific. This is also the era when my uncle Leonard flew a Supermarine Walrus from a Royal Navy cruiser in the Mediterranean. Hard to believe that this ugly duckling, a biplane flying boat, came from the same company as the beautiful Spitfire. The only modern flying boats of any size are water-bombers such as the Bombardier 415.
Tech Level: Same as above, Dieselpunk. Also ripe for Alternative History.
Appeared In: More than one Adventure Story. I think I remember a sort of airborne Murder on the Orient Express thing. In Spec Fic, Ian Sales set out to write an SF short story, with interesting but unconventional results.
For Your Plot: This harks to an amazing era, when the Pan-Am Clipper was the Concorde of its day. Millionaire passengers, autocratic Captains, eastern intrigue and typhoons. Do me.