A modified Boeing 747 is to take off from Newquay in Cornwall on Monday evening for the first-ever launch of an orbital satellite from western Europe.
The Virgin Orbit mission, which will turn the surfing town into Britain's first spaceport, begins with a horizontal launch, wherein a plane carries a rocket part-way into the sky.
The modified 747 will take off from Spaceport Cornwall before releasing a rocket at 35,000 feet over the Atlantic Ocean.
The launch will be a landmark one for the UK, marking its arrival in the global space launch market.
Melissa Thorpe, head of Spaceport Cornwall, said: "What we've seen over the last eight years is this building of excitement towards something very aspirational and different for Cornwall, something that started off as a project that not a lot of people really believed was ever going to happen.
"What I think people have seen here in Cornwall is a small team that lives and breathes this county deliver something quite incredible."
Virgin Orbit, which is part-owned by billionaire Richard Branson, has said nine satellites will be deployed into lower Earth orbit (LEO) from the LauncherOne rocket.
The new spaceport gives Europe options for launching small satellites at a critical time, after the Ukraine war cut access to its use of Russian Soyuz vehicles.
The conflict has highlighted the importance for tactical military purposes of smaller satellites, like those being launched from Newquay, that can get into low orbit at much shorter notice than bigger ones.
Dan Hart, Virgin Orbit's chief executive, said the satellites – which are the size of breakfast cereal boxes – would fulfil tasks such as maritime research and detecting illegal fishing and piracy, as well as national security.
"We can all personally connect with one or more of the satellites that are flying on this mission," he said.
Asked what the biggest difference between launching in Cornwall and California was, he joked: "Pasties versus hamburgers, it's a significant shift."
The aircraft, named Cosmic Girl, is expected to take off at some point between 9.40pm and 11pm, but this is dependent on the weather and "health of the system".
Virgin Orbit has said there are back-up dates available for later in January.
"Assuming that everything continues to look good we're currently tracking well for launch," a Virgin Orbit spokeswoman said on Sunday.
Space enthusiasts with tickets for the launch, which is called 'Start Me Up' after the Rolling Stones song, will watch from a viewing area across the runway before attention shifts to a live stream on a big screen.
Virgin Orbit's focus on LEO satellites is at the other end of the scale from the large satellites in geostationary orbit that are launched by vertical rockets.
The LEO sector is growing rapidly, spurred by satellite broadband companies such as Elon Musk's Starlink, Amazon and London-headquartered OneWeb.
The smaller satellites are also used for climate change observation, urban development and security purposes, and Britain hopes the new spaceport will boost its space economy.
The country has a large space industry employing 47,000 people, who build more satellites than anywhere outside the US, but those have had to travel to spaceports in the US, French Guiana or Kazakhstan before they can make it into orbit.
Watch: Virgin Orbit gears up to be Britain's first-ever space launch