Delta to join S&P 500 after close of trading on September 10

(Reuters) - Delta Airlines will join the S&P 500 index after the close of trading on September 10, replacing BMC Software , Standard & Poor's said on Friday. Shares of Delta, the second largest carrier behind United Continental , rose 4.6 percent to $20.80 in after-hours trading. BMC will be replaced in the index on Tuesday because Bain Capital LLC is expected to complete its acquisition of BMC on or around that day, S&P said. Delta, which filed for bankruptcy in 2005 and acquired Northwest Airlines in 2008, has improved profits and reduced debt in recent years. It last paid a common stock dividend in 2003, and its last share buyback plan was in 2000. To cut costs, Delta has been retiring fuel-guzzling planes and acquiring used aircraft, and it bought a Pennsylvania oil refinery last year. In May, Delta said it planned to return $1 billion to shareholders over the next three years, starting with its first dividend in a decade and a $500 million share buyback program. The initiatives are part of a five-year plan that seeks to generate as much as $5 billion in value for investors. Airlines, which weathered a tough decade after the September 11, 2001, attacks, have gained more solid financial footing and are now focusing on improving their investment potential. (Reporting by Nicola Leske; Editing by Bernard Orr and Leslie Adler)