Thursday's launch - originally slated for Wednesday but put on hold because of "high altitude wind shear" - marks the first big step in Musk's plan for "rebuilding the internet in space," as he put it in 2015.
In addition to competing with typical internet providers, Starlink could deliver connectivity to rural communities without the lag they're accustomed to.
Critics - including broadband competitor OneWeb, which has already received FCC approval for its own constellation of low-Earth-orbit satellites - worry that all those SpaceX satellites whirring around would pose "danger from orbital debris," and risk collisions with other satellites already in orbit.
In a letter to the FCC, SpaceX's attorney said the company is confident Starlink is "more than capable of operating safely" and called OneWeb's concerns "self-serving and anti-competitive."
The SpaceX satellites to be delivered to low-Earth orbit this week, Microsat-2a and Microsat-2b, are scheduled to be carried aboard a Falcon 9 rocket set for launch from Vandenberg AFB in California Thursday morning, at 6:17 a.m. local time.
They'll be monitored by receivers in California, Texas, and Washington state.
SpaceX still needs formal approval for the rest of the Starlink system, but FCC chairman Ajit Pai has already called on his colleagues to support the company's efforts to "unleash the power of satellite constellation to provide high-speed internet to rural Americans."