SpaceX CEO Elon Musk took aim at Jeff Bezos on Wednesday, as the two continue their increasingly competitive space race.

“Filing legal actions against SpaceX is *actually* his full-time job,” Musk tweeted about the Blue Origin executive, echoing an earlier tweet that referenced Bezos’ retirement as Amazon’s CEO.

The tweet comes a day after SpaceX issued a response to a protest letter from Amazon about SpaceX’s plans to expand its Starlink network of internet satellites.

In the letter to the FCC, SpaceX called Amazon’s request a “continuation of efforts by the Amazon family of companies to hinder competitors to compensate for Amazon’s failure to make progress of its own.”

Amazon’s initial letter called for the FCC to require SpaceX to submit a new proposal because its proposal offered two options for how it would expand its satellite system, instead of one.

The SpaceX letter pointed out that Bezos’ companies including Amazon and Blue Origin have averaged about one complaint every 16 days over the past year. It said that the lawsuit’s have “become a bigger bottleneck than the technology,” harking back to Bezos’ own words regarding the impact of regulatory issues like lawsuits and protests on the progress of his space company, Blue Origin.