The FCC has granted SpaceX permission to go forward with plans to offer a direct-to-phone version of its Starlink satellite internet service, with T-Mobile as its provider and a few provisos in place.

The proposal dates to summer 2022, when SpaceX and T-Mobile first announced that they were pursuing the ability for the mobile provider’s customers to get Starlink access on their phones. At the time, they said they expected the service to start in 2023, but here we are at the end of 2024 and it’s only just now getting regulatory approval.

Still, it’s a coup for Starlink, which will get its foot in the door in the US market before its rivals, including existing direct-to-phone satellite provider Lynk, which is already in orbit but has no US commercial partners. SpaceX will be able to use certain wireless bands, in close partnership with T-Mobile as the terrestrial operator, to allow customers with compatible devices to communicate.

But as the leaders of the companies pointed out at the announcement, it’s more than just getting approval and turning on the service. Non-trivial engineering problems must be solved to sync a phone up with a cell “tower” that’s actually on a satellite hundreds of miles away and going thousands of miles per hour. But they appear to have figured this part out: the company demonstrated a video call six months ago, and as the FCC notes, direct-to-phone connections were allowed during hurricanes Helene and Milton to allow disconnected areas better access to emergency services.

The FCC states in its filing (first reported by Bloomberg) that the upside is clear:

We find that SpaceX and T-Mobile’s SCS operations will yield many benefits, including an increase in access to emergency services in areas where consumers would otherwise not have the capability to access a terrestrial network to call or text 911, as evidenced, for example, through SpaceX’s provision of emergency SCS in areas affected by Hurricanes Helene and Milton.

There are a few limitations on how this type of service (which the FCC calls “supplemental coverage from space,” or SCS) can work. Right now it officially has to operate as an extension of an existing terrestrial provider, in this case T-Mobile. That’s because the regulations on how you broadcast stuff in space are different from those for how you broadcast stuff to and from a phone (as opposed to a base station antenna). AT&T, for its part, is partnering with AST SpaceMobile.

SpaceX must also be sure that its service does not interfere with other services on the ground, while the ground services do not have to worry about whether they might interfere with the satellite signals.

As for latency and signal power, every kilometer of altitude matters — and Starlink is up at the 530 km level. Fortunately for SpaceX, the FCC has authorized it to operate any of the remainder of its 7,500 approved satellites at altitudes of 340, 345, 350, and 360 kilometers. Those in the know will have noticed that this is rather close to the lower limit of the International Space Station’s orbit (370 kilometers) — and indeed, SpaceX will need to coordinate any deployment below 400 km with NASA.

It is notable, reading through the filing, how many notional competitors to Starlink — Amazon’s Kuiper, DISH, Omnispace, TerreStar, and more — filed objections to its applications, no doubt to delay it. This is not to say that their objections are without substance, but the FCC was clearly not convinced by many of them, or was happy to let SpaceX cure its applications with the appropriate remedies.

Before long, “no signal” will be a thing of the past — and fortunately, many of those involved in this space tend to favor universal access for emergencies and the like, rather than privileged access for streaming Netflix at Burning Man. That said, nothing in the filing indicates when SpaceX and T-Mobile will bring the service online or at what cost.