This milestone is 'the first major test for whether Starlink will be here for the long haul,' according to projections from analyst firm Quilty Space.

Astronomers are concerned about the potential impact of SpaceX Starlink satellites blocking out the view of space.

Spaceflight doubleheaders are far from a novelty for SpaceX these days. On March 30, for example, the company launched two missions — a Starlink batch and the Eutelsat 36D telecommunications satellite — less than four hours apart, both of them from Florida's Space Coast.