First launch Q1 2019 ? Let's hope so, but lets keep hold of reality, rockets and space flight are risky. Look at the failures Elon Musk had to endure before succeeding in a successful test flight.
In the case of Virgin :
The Virgin Galactic test flight ended in disater in Oct 2014 killing one pilot and seriously injuring the other. No further powered testing was carried out until Apr 2018. Only a 30 second burn of its rockets. Pfft. Since then nothing...
Virgin Orbit: They will be launching SAS's nanos using Cosmic girl piggy backed with a 747. Well of course the 747 works, that's just a modification of a highly successful plane that was first put into commercial service in 1969.
But ..... Cosmic girl hasn't even made a rocket powered test flight yet ! After a delayed testing campaign it is now supposedly due to be tested in August 2018. If that blows up then more delays or alternative launching will have to be considered.
Just saying Richard Branson's timelines seem to be extremely elastic
