Virgin Orbit will be air-launching their LauncherOne rocket from a former Virgin Atlantic Boeing 747 for the first time. LauncherOne is another competitor in the field of smallsat launch providers such as Rocket Lab from New Zealand with their Electron rocket and their direct competition Pegasus. Pegasus, by Northrop Grumman, is another air-launched rocket . Both air-launched rockets can carry approximately 500kg to LEO, but Pegasus is 4 to 5 times more expensive per launch.
A significant advantage of air-launched rockets is that they can launch from anywhere and reach a variety of different orbits. Virgin Orbit even offers a three stage option for interplanetary missions.
This maiden flight will carry a simulation mass of 500 kg.
The carrier aircraft Cosmic Girl will take off from Mojave Air and Space Port and release LauncherOne over the Pacific ocean.
Summary by Scott Manley: YouTube
Note: Virgin Orbit is a different company than Virgin Galactic, which is is planning on offering sub-orbital space flights for passengers.
There will be no live stream available but Virgin Orbit will provide footage afterwards.
Stay up to date: virginorbit.com
Useful links to stay up to date on launches:
Spaceflightnow.com: Launch Schedule
Everyday Astronaut: Prelaunch Previews
NASA Spaceflight nasaspacefight.com
Be aware, this is rocket surgery.
Small disturbances can lead to postponed launches. Making sure everything is just right is way cheaper than risking big fireworks.