Billionaire Rakesh Gangwal, Co-founder of InterGlobe Aviation (IndiGo), has purchased shares worth $107 million (₹900 crore) in Southwest Airlines. He bought 3.6 million shares of the American airline for $29-$30 apiece, according to SEC filings. Gangwal, who was appointed to Southwest's board in July, said that he made the purchase as soon as the stock trading window for insiders opened.