After years of working through a thicket of regulatory matters, Virgin Orbit says it is finally ready to fly its LauncherOne rocket from the United Kingdom.

If all goes well, the modified Boeing 747-400 Cosmic Girl aircraft will take off from a spaceport in Cornwall on Monday evening, with a launch opportunity at 5:16 pm ET (22:16 UTC) over the Atlantic Ocean. This “Start Me Up” mission, bound for low Earth orbit, will carry satellites from seven customers in both the United States and United Kingdom.

The air-launch mission has received considerable attention in the United Kingdom because it is being advertised as the first-ever orbital launch from the nation. It will, in fact, be the first orbital satellite launch from the UK or Western Europe. However, it will not be a vertical launch from UK soil. Spaceports capable of such launches are under construction in several locations around the nation but probably will not be ready for an orbital launch this year. And unlike British launch companies that aim to use those spaceports, Virgin Orbit’s technology was developed, built, and tested in the United States.