Airlines are reporting better unit revenues for the tail end of summer, a sign customers will continue to have to shell out more to fly in the coming months.Alaska Airlines on Thursday raised its third-quarter profit forecast to a range of $2.15 to$2.25 per share from a previous outlook of no more than $1.60 per share. It also said it expects unit revenue to rise by as much as 2% after previously estimating flat to "positive" unit revenue.Delta Air Lines said domestic and trans-Atlantic unit revenue would ...