United Technologies Corp. Tuesday unveiled a $12 billion share-repurchase plan, partly funded through the sale of its Sikorsky helicopters business, as the company said it continued to face sagging sales in its latest quarter. The Farmington, Conn.-based maker of Pratt & Whitney jet engines, Otis elevators and Carrier air-conditioning equipment reported a 5.6% decline in third-quarter sales amid currency headwinds and engine-delivery delays.