Shares of Boeing Co. (NYSE:BA) are trading lower Monday after the U.K.’s Competition and Markets Authority (CMA) announced a formal investigation into the company's proposed $4.7 billion acquisition of Spirit AeroSystems.

What To Know: The deal, which Boeing has framed as critical to stabilizing its supply chain and improving production quality, now faces a regulatory hurdle that could delay or block the transaction, according to The Wall Street Journal.

The CMA initially launched a preliminary review last week and has since escalated the matter into a formal Phase 1 probe. Regulators are examining whether the acquisition could reduce competition in the U.K. aerospace sector, with a decision on whether to proceed to a deeper investigation expected by Aug. 28.

The acquisition would give Boeing greater control over Spirit's fuselage manufacturing operations, components that have been at the center of quality issues. Company executives have publicly argued that bringing Spirit, which split from Boeing roughly 20 years ago, back in-house would help address longstanding issues in safety and quality control.

The antitrust review, however, introduces a level of uncertainty that is weighing on investor sentiment. The added scrutiny from U.K. regulators comes as Boeing continues to navigate quality and production challenges across multiple programs, and any disruption to its supply chain recovery plan is viewed as a potential setback.

While the market reaction remains moderate, the regulatory probe highlights the geopolitical and competitive complexities Boeing faces as it tries to streamline its manufacturing process through vertical integration.

BA Price Action: Boeing shares were down 2.32% at $209.59 at the time of publication Monday, according to Benzinga Pro.

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