(Bloomberg) — Hexcel Corp., a key supplier to Boeing Co., tumbled the most in four years after the company’s head-scratching CEO change drew concern on Wall Street.

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Tom Gentile will take over as Hexcel’s chief executive officer on May 1 and likely join the board soon after, the company said late Tuesday. Current CEO Nick Stanage will become executive chairman until retiring at the end of the year.

The appointment comes about six months after Gentile abruptly resigned as head of Spirit AeroSystems Holdings Inc., another supplier to aircraft makers. Spirit and Boeing have come under deep scrutiny in recent months over manufacturing quality problems spanning multiple plane models.

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Truist Securities analyst Michael Ciarmoli called the hiring “unnerving” in a client note and said it’s “one of the more curious moves we have seen” in the aerospace industry. Spirit “has a long history of quality problems, inability to generate cash and inability to drive margin expansion,” he said.

Northcoast Research analyst Chris Olin said Gentile’s final years at Spirit “could become the real point of contention” for investors. Northcoast and Bank of America each downgraded the stock following the CEO announcement.

Hexcel’s shares plunged as much as 13% Wednesday in New York, the biggest intraday slide since March 2020.

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