Musk has bought the missing piece of spectrum for satellite communications.

On Thursday, SpaceX announced that it had agreed to acquire a nationwide portfolio of 800 MHz low-band spectrum assets from Grain Management, with up to 14 MHz of paired bandwidth. The announcement was blunt: these low-frequency bands can penetrate walls and trees, and mainstream phones can access them without modification, filling the remaining technical gap for Starlink Mobile. Musk later called it a very large deal on social media.

The reaction was swift. Shares of the traditional U.S. telecom Big Three—AT&T, Verizon, and T-Mobile—tumbled after hours.

The timeline makes things clearer. Just last week, the three companies formed a joint venture focused on using satellites to fill mobile coverage gaps, leaving Starlink out. Less than a week later, Musk had snapped up the spectrum himself. The deal still requires regulatory approval.

The source of pressure on terrestrial carriers has become clear in recent days. A rocket company is moving in on their turf, and the owner of $TSLA has now reached into the toll road.