X owner Elon Musk, following through on a legal threat he made two weeks ago, filed an antitrust lawsuit on Monday accusing Apple and OpenAI of colluding to make the artificial intelligence company’s ChatGPT rank higher than his Grok chatbot in the iPhone maker’s app store.

The lawsuit, filed in the U.S. District Court for the Northern District of Texas, alleges the two companies are maintaining monopolies on the smartphone and generative AI markets and effectively shutting out competition.