For most of human history no-one suspected there is any kind of lightning apart from the familiar kind we can see from the ground. But in 1989 researchers testing a low-light TV camera accidentally captured a recording of what was later name a 'sprite and later that year a similar phenomenon was filmed from the Space Shuttle.

It is not surprising they hadn't been observed before, because they are brief duration (milliseconds to seconds) and to see them an observer needs to be able to see the top of a stormcloud, which means from a favourable ground location, an aeroplane, or space.

I can remember reading about them, probably in Scientific American, soon after they were discovered,  and being very surprised and excited.

Since then many different kinds of what are termed Transitory Luminous Events (TLEs) have been describes; as well as Sprites there are Jets, Giant Jets, Elves, Pixies, Ghosts, Troll and Gnomes.

Here is a diagram ^[1]  from the National Oceanic and Atmospheric Administration, showing what some of them look like, their scale, elevation, and relationship to ordinary lightning.

Here is a recording of some sprites ^[2]

And here is one of a giant jet, taken from the International Space Station. We can get a rough idea of its size by comparing it with the curvature of the Earth, visible  in the background, and it must indeed have been truly gigantic.

Credits

[1] Transient luminous events (TLEs), National Oceanic and Atmospheric Administration (NOAA), Public Domain.

[2] Cropped from Red sprite above Hungary, MTA Geodéziai és Geofizikai Kutatóintézet / Geodetic and Geophysical Reseach Institute of the Hungarian Academy of Sciences. Licensed under Creative Commons.

[3] Photograph of a gigantic jet taken from the International Space Station by astronaut Nichole Ayers, Public Domain.