Electric Aircraft: any flying machine that is propelled by an electric motor. Naturally, the first example was a dirigible (in the 1800’s) because the lifting gas took care of the battery weight and speed wasn’t a requirement. There were some experimental conversions of airplanes in the 1970’s, mainly led by sailplanes employing electric power as a supplement, and leading to some commercially available small aircraft, but it was 21st century before solar power, improved battery chemistry and fuel cell technology began to make serious inroads. At the time of this writing, electric aircraft are still on the fringes. Records are being set, but the prospect of buying a ticket on an electric airliner is decades away. Speaking of records, here are links to the website of Solar Impulse and their latest news: their solar powered flight around the world should resume before the A to Z Challenge is over.
Tech Level: Steampunk, if you include dirigibles. Solarpunk could make use of either solar-powered airships or airplanes.
Appeared In: I have yet to find a definitive example. Might be a case of truth is more exciting than fiction. Comment if you know a good one.
For Your Plot: Electric aircraft could be anything from a reliable means of transport that lends flavour to your solarpunk world-building, to an edgy, cobbled-together means of moving about in a post-apocalyptic world.