The airline's latest news could have been better, but the stock remains at an excellent value on balance.The recent report and guidance from Delta Air Lines (DAL 6.79%) were slightly disappointing for more than one reason. However, they must be examined in the context of the stock's valuation and underlying earnings trends. In doing so, it's clear that there's a robust case for buying the stock despite its 22% run-up since the start of August. Here's the lowdown.Delta Air Lines' mixed newsStarting with the ...