Virgin Orbit's "Cosmic Girl" took off from Newquay's spaceport in Cornwall for Western Europe's first satellite launch late on Monday.
The Virgin Orbit jet carrying the 70-foot (21-metre) rocket containing nine satellites took off from a spaceport in Cornwall, southwest England, at 2202 GMT.
The rocket will detach from the aircraft and ignite at a height of 35,000 feet over the Atlantic Ocean to the south of Ireland at around 2300 GMT, before later discharging the satellites.
The aircraft will then return to Spaceport Cornwall, a consortium that includes Virgin Orbit and the UK Space Agency, at Cornwall Airport Newquay.
The launch is the first from UK soil. UK-produced satellites have previously had to be sent into orbit via foreign spaceports.
If successful, the UK will be one of only nine countries that can launch craft into Earth's orbit.
"Joining that really exclusive club of launch nations is so important because it gives us our own access to space... that we've never had before here in the UK," Spaceport Cornwall chief Melissa Thorpe told BBC television on Monday.
Hundreds of people watched the launch, named "Start Me Up" after the Rolling Stones song.
"There's two stages to it... two bits of excitement, really, the takeoff and then the deployment of the rocket," Thorpe added.
The satellites have a variety of civil and defence functions from sea monitoring that will help countries detect people smugglers trafficking migrants to space weather observation.
The number of space bases in Europe has grown in recent years due to the commercialisation of space.
For a long time, satellites were primarily used for institutional missions by national space agencies but most of Europe's spaceport projects are now private sector initiatives.
The market has exploded with the emergence of small start-ups, modern technology making both rockets and satellites smaller, and the rapidly growing number of applications for satellites.
Some 18,500 small satellites -- those weighing less than 500 kilograms (1,100 pounds) -- are expected to be launched between 2022 and 2031, compared to 4,600 in the previous decade.
Campaigners, however, criticised the launch.
"Space is the new frontier for military escalation and spending with no real public scrutiny or accountability," said Campaign for Nuclear Disarmament (CND) general secretary Kate Hudson.
Drone Wars director Chris Cole denounced a "space arms race which will inevitably lead to greater risk of instability and conflict".
