You could be forgiven for thinking a rocket had been launched over Gingin yesterday, but the Bureau of Meteorology has confirmed the unusual cloud formation was part of a very common phenomenon.
The formation looked as if a missile had been fired, with the thin stream of cloud stretching up out of sight.
Residents posted photos and video to social media showing the cloud yesterday afternoon, and speculated on its origins.
Unfortunately, the formation's origins were not as exciting as proposed "unidentified flying objects".
Bureau of Meteorology duty forecaster Angus Moore said the cloud was more commonly known as a condensation trail or "contrail".
"Contrails develop in the wake of high-flying aircrafts' exhaust streams from their engines as water molecules in the exhaust condense to form a water vapour- like cloud," he said.
"Only high-flying aircraft that are flying over Perth are likely to be observed with condensation trails, and because Perth is so remote, this does not often occur."
So while it wasn't a UFO or a secret military missile, it was still pretty cool.
