Balloon: One of the oldest forms of aviation pioneered by humans. There are two main kinds, the hot-air balloon popular at festivals, and the lifting-gas balloon, filled with helium or hydrogen. The former requires fuel, so duration is limited. The latter is more expensive, but better suited to longer flights such as ocean crossings. There are also hybrid designs. Balloons can be navigated by climbing and descending to take advantage of variations in the wind. This is as much art as science; balloon pilots relish the challenge.
Tech Level: The Montgolfier brothers famously flew a hot-air balloon in 1783. The principle requirement is a fine, nearly airtight fabric, such as silk or paper. The Montgolfiers used sackcloth lined with paper. I class the balloon as Clockpunk or lower.
Appeared In: Jules Verne’s Around the World in Eighty Days, published in 1873. You can’t ask for a finer pedigree than that.
For Your Plot: Wonderful potential to take your hero to the wrong place, and ample opportunity to mess him up with minor injuries from a bad landing, or worse trouble from an unplanned landing in the water, mountains, or orc territory.
Biplane: A fixed-wing airplane with two wings, one (approximately) above the other. In its heyday during World War I, it offered designers a strong yet compact design, as the two wings could be braced together with struts and flying wires. That creates drag, so the biplane tends to be slow, and the design is all but extinct these days. A fabulously quirky example was the Sopwith Camel. It had no brakes, no throttle, and a rotary engine: the designers chose to bolt the propeller to the engine block and fix the driveshaft to the airframe. The whole engine spun while the plane stood still. Great for cooling, but no muffler, so sneaking into enemy territory was not an option. See a wonderful eight minute video here.
Tech Level: Post-industrial, because a light powerplant such as a reciprocating engine is needed. I class it as Dieselpunk.
Appeared In: Storming, by K.M. Weiland.
For Your Plot: Many biplanes had open cockpits. Subject your hero to freezing wind, hypoxia and bugsplats. Get her lost when the map is blown overboard. A stylish goggle-tan makes her stand out in the crowd.