I fly in the military, the following was told to me by a friend that's a Delta 757/767 first officer. I'm not saying that it is necessisarily true, but apparently it's a story that's making the rounds at Delta:

Currently Delta pilot rules allow them to volunteer to fly on what they call a ''Green Slip", in a nutshell the company uses a greenslip in the extreme instance where - for whatever reason - they don't have a pilot to fill a flight, i.e. the originally scheduled pilot is unavailable and all of the pilots on Reserve (the guys that are already designated to be fill-ins when other pilots call in sick etc), and basically the company would otherwise have to cancel the flight if they can't round up a qualified warm body to fly the airplane. A pilot can volunteer to take a Green Slip during their off-time and/or even when they are already scheduled to fly something else. Why would a pilot volunteer to fly on their off time or when they are already scheduled to fly another trip? That's easy - because they are paid DOUBLE their regular hourly wage. With so many Delta Captains taking early retirements - in pre-emptive moves to take their retirement money in a lump-sum while it it still there rather than perhaps be left holding the bag in the event of a UAL-like pension fiasco - Delta has recently been critically manned in some pilot postitions and as a result supposedly one Captain (more than likely a 777 or 767ER guy) recently had a month where he flew on Green Slips so much that he made $60K.

If this is true no wonder this company is on thin ice...