Problem with antitrust hammers is that once you've chopped Boeing into bits you don't end up with a competitive market with lots of new aircraft designs, you end up with a global Airbus monopoly on aircraft over 150 seats and the few surviving bits of Boeing competing to sell into its supply chain...

Airframers really aren't that vertically integrated as companies go. But it turns out the business of designing, certifying and selling an aircraft (and managing complex multinational supply chains) is hard, and airlines don't want 6 competing types of narrowbody in their fleet, they want one type of narrowbody in their fleet with an abundance of type-rated pilots, multiple maintenance options and a robust aftermarket.