Wesco Aircraft Holdings, the Carlyle Group-controlled aerospace equipment supplier in Valencia, priced an initial public offering of 21 million shares at $15 a share, below initial expectations.

Wesco Aircraft did not sell any shares in the offering. The IPO, which initially was expected to price between $15.50 and $17.50 per share, raised $315 million for its early backers, which include the Carlyle investment firm and Wesco Chief Executive Randy Snyder. The shares are expected to begin trading Thursday on the New York Stock Exchange under the ticker symbol “WAIR”.

The selling stockholders have granted the underwriters an option to purchase up to 3.15 million additional shares at the initial offering price to cover any overallotments.

Wesco Aircraft said it was founded in 1953 by Snyder’s father, and has grown to become one of the world’s largest distributors and providers of aircraft hardware, bearings, tools and more recently, electronic components and machined parts. It employs more than 1,000 people in 28 locations in 10 countries, and had net sales of $656 million in fiscal 2010. As of Dec. 31, Carlyle, through its Falcon Aerospace Holdings LLC, owned 83.8 percent of outstanding common stock.

Barclays Capital Inc., Morgan Stanley & Co. LLC, BofA Merrill Lynch, J.P. Morgan Securities LLC and William Blair & Company, L.L.C. were joint book-running managers of this offering.