Shares of Boeing Co. ( 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 ( BA ) 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 ( BA ) 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 ( BA ) 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 ( BA ) 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 ( BA ) faces as it tries to streamline its manufacturing process through vertical integration.

BA Price Action: Boeing ( BA ) shares closed Monday down 2.34% at $209.53, according to Benzinga Pro.

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