I won't sugarcoat this: Traditionally, airlines have not been great investments, at least not for those interested in equities. Still, there's strong reason to believe that won't always be so.Delta Air Lines (DAL 0.14%) is an excellent example of a stock that can buck the trend and remain the pick of the transportation sector. Here's why the stock is a great value.Equity investors and bond investors view airline stocks differentlyWith even Warren Buffett having lost money on airline stocks in the past, it m ...