Photo: A SpaceX Falcon 9 rocket stands vertical on the launch pad at Vandenberg Air Force Base — public domain image donated by SpaceX, via Wikimedia Commons.

Elon Musk wants to add a fourth major phone company to America — and this time the network would come from space.

Bloomberg, via Reuters, reported Thursday that SpaceX is in talks with Crown Castle for access to at least 80,000 cell sites — the ground infrastructure it would need to build its own wireless carrier from scratch, a direct challenge to AT&T, Verizon, and T-Mobile.

Wall Street took the threat seriously on Friday: AT&T fell 5.6%, T-Mobile dropped 5%, and Verizon slipped 1.6%, while Crown Castle jumped 11.6%.

The carriers declined to comment, but analysts are already doing the math on what a satellite-backed fourth carrier could mean for your phone bill — and for coverage in places the big three still leave behind.

For a company that started by selling internet from orbit, selling you the cell plan itself is the obvious next step.