SpaceX Chief Executive Elon Musk said on Thursday that the company's acquisition of 800 MHz spectrum will mark a major milestone in delivering satellite-to-cellular connectivity services across the United States.

Musk reposted a message from Tesla investor Sawyer Merritt on social platform X and commented: "This is the final key piece of the spectrum puzzle." Merritt noted in his post that the 800 MHz spectrum acquired by SpaceX will enable "better indoor coverage" and provide "signals capable of penetrating walls and other obstacles." Musk added that this spectrum will help SpaceX deliver "comprehensive mobile signal coverage" in the United States.

Musk also responded to investor and All In podcast host Chamath Palihapitiya, who had quoted a post Musk published on X. Palihapitiya said: "This is a big deal." Replying to the Social Capital founder, Musk said: "To the casual observer, this may not seem like much." He added: "But for those who understand the spectrum wars, this is nothing short of an earthquake."

Following the news, telecom company stocks fell broadly. AT&T Inc (NYSE: T) shares dropped 6.59% to $23.23 in overnight trading after closing Thursday's session up 1.63%. Verizon (NYSE: VZ) shares fell 5.70% to $43.71 in Thursday overnight trading. T-Mobile US (NASDAQ: TMUS) shares also declined 6.10% to $160.86 in overnight trading.

The 800 MHz band is low-band spectrum, which compared with high-band spectrum can transmit signals over longer distances and penetrate buildings and other obstacles more effectively. SpaceX has agreed to acquire a nationwide spectrum asset from Grain Management, including up to 14 MHz of paired spectrum within the 800 MHz band. The company said this low-band spectrum will complement its existing 2 GHz spectrum, helping "Starlink Mobile" provide network connectivity for indoor devices.