It's not limited to DL. I need to go from SJC to DTW next week, and every seat from SJC to ORD is booked. I suppose fares are low enough to attract leisure travelers. But I would not advise traveling standby this summer.

On a side note, with every flight full, the Big Six are still bleeding money. If I was a shareholder of any importance, I would want to fire the boards and management of these companies. Although I know they have higher cost structures than the money-making "no frills" carriers, there has to be something they can do. They have been slicing employee compensation to the bone. Maybe the management is highly over-compensated...