Ski-resort operator Vail Resorts ( MTN - Get Report) said Chairman and Chief Executive Adam Aron is resigning effective June 28 after 10 years of running the company. Vail said Monday that Aron plans to offer his assistance to the company, if he's asked by the board of directors, after he vacates his posts. The Colorado-based company's board plans to immediately begin searching for a successor. Vail said it will consider both external and internal candidates. Vail operates some of the best-known ski mountains in the U.S., including Vail, Beaver Creek, Breckenridge and Keystone in Colorado, Heavenly in California and Nevada, and the Grand Teton Lodge in Jackson Hole, Wyo. Shares of Vail were down 83 cents, or 2.6%, to $31.64.