AT&T is petitioning the FCC to block rival T-Mobile US’s plan to use SpaceX’s satellite service to boost its mobile network coverage.

The US operator hopes the regulator will put the brakes on T-Mobile’s plans – at least for now – citing possible interference issues and the breaking of spectrum allocation rules, it explained in a filing published on Friday. The FCC had called for comments after T-Mobile and SpaceX requested authorisation to deploy supplemental coverage from space, or SCS, to supplement the mobile operator’s terrestrial network using SpaceX satellites.

“The FCC’s rules do not permit SpaceX’s proposed use of T-Mobile’s terrestrial spectrum, and Applicants fail to even request—much less justify—rule waivers that would be necessary to authorize their proposed SCS authorizations,” AT&T’s filing reads.

“More broadly, the Applicants’ technical showings are woefully insufficient regarding the risk of harmful interference posed by their planned SCS deployments. SpaceX and T-Mobile’s applications fall far short of meeting the threshold for waiver and cannot be granted in their current state,” it says.

T-Mobile announced its intention to work with SpaceX to fill coverage gaps in its US network last August, its focus being on reaching remote areas that are difficult to cover with traditional mobile networks. Specifically, there are well over half a million square miles of US landmass with no mobile signal, as well as vast stretches of ocean, it said at the time.

The companies pledged to create a new network, broadcast for SpaceX’s Starlink satellites using T-Mobile’s mid-band spectrum – its G Block frequencies, that is – to offer a satellite-to-cellular services providing near complete coverage “almost anywhere a customer can see the sky.”

Using LEO satellites, such as the Starlink constellation, to boost cellular network coverage clearly makes a lot of sense. So much so, that AT&T is at it too.

It has inked a deal with AST SpaceMobile with a similar goal, and was involved in the latter’s biggest testing milestone earlier this year; AST SpaceMobile was excited to announce a month ago that it had successfully carried out a direct voice call between the US and Japan, via its LEO satellite constellation, using standard smartphones and AT&T spectrum.

AT&T mentions this and other trials with AST SpaceMobile in its FCC filing as examples of its commitment to demonstrate that their collaboration will not cause interference with authorised terrestrial systems. It also highlights its own regulatory applications, the implication being that it and AST SpaceMobile are doing it right, as well as pointing out T-Mobile and SpaceX’s apparent lack of actual progress in their deployment thus far:

“To date, it does not appear that SpaceX and T-Mobile have begun testing any SCS deployments,” it states.

It could be that AT&T is genuinely concerned about its rival’s rollout plans; it responded to the FCC’s call for comments in its capacity as a holder of adjacent broadband PCS C Block spectrum, after all.

But it is perhaps more likely that AT&T is using every tool at its disposal to get ahead in this space race. After all, the first mobile operator to be able to provide decent mobile coverage in hard-to-reach areas will surely have an advantage when it comes to signing up customers.

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