The SpaceX mission, masterminded by billionaire Elon Musk, marks the 62nd flight of the Falcon 9, a rocket designed to land back on Earth so it can be used again.
The rocket’s launch, which was trailed by a blue and white glow in the night sky, left many locals questioning if they were witnessing a UFO.
Some took to Twitter to describe “a huge burst of light”, while another user’s concern resulted in contact with the police department of Modesto, California.
The Air Force last week advised residents on the central California coast they might see multiple engine burns by the first stage and hear one or more sonic booms as it returned.
The spacecraft’s landing near its concrete launching pad at the Vandenberg Air Force Base west of Los Angeles was the 30th landing of a rocket booster for the company and the 17th launch of the year, putting it on track for its stated ambition of 24 launches in 2018.
The private spaceflight company has launched multiple satellites and shuttled supplies and science gear to the International Space Station, with its Falcon 9 being the first spacecraft from a private company to reach the station in 2012.