The first rocket launch from UK soil failed because of a premature shutdown in the rocket that prevented LauncherOne from reaching orbit, Virgin Orbit has said.
The opening part of the mission went according to plan, the company said, as its plane took off from Spaceport Cornwall, Britain's first such site, at Newquay Airport.
A converted Boeing 747 named Cosmic Girl flew to 35,000ft over the Atlantic Ocean off Ireland's southern coast, just before 11.15pm on Monday.
There it jettisoned the 21-metre-long rocket containing nine small satellites, which would have been the first launched into orbit from the UK, or anywhere in western Europe, towards space.
But the organisers of the Start Me Up mission soon identified an "anomaly" and said LauncherOne had failed to orbit.
The company, founded by Sir Richard Branson in 2017, said in a statement that initial data suggested the first stage of the rocket performed as planned, that it reached space altitudes, and that stage separation and ignition of the upper stage occurred in line with expectations.
But later in the mission, at an altitude of around 180km (112 miles), the upper stage experienced an anomaly which prematurely ended the first burn.
This ended the mission, the company said, with the rocket components and payload falling back to Earth within the approved safety corridor without ever achieving orbit.
It left around 75,000 people who watched a livestream of the event, and thousands more who trekked to the Cornish resort for the launch, disappointed.
The latest failure came after technical issues had prevented its first planned take-off attempt before Christmas.
But the US-based company has not been deterred, adding that it was already in "active discussions" with government and customers about returning to Spaceport Cornwall for another go as early as later this year.
In the meantime, Virgin Orbit has launched a formal investigation into the source of this week's failure.
The Cornwall spaceport is the first to get a licence in the UK, but more could follow in the coming years as demand from businesses to launch small satellites increases.
Ian Annett, deputy CEO of the UK Space Agency, said Snowdonia in North Wales and Glasgow Prestwick Airport were among seven sites identified.