Found out what happened that I was able to check my bags early at RDU yesterday.
Several young Marines were flying Airtran to Pensacola to continue their training. The supervisor opened a lane to get them boarding passes and take their luggage.
It was coincidental that I was on the same flight, so my agent tossed my luggage onto the belt knowing that they had already started a cart for the military bags.
It seems that there is only so much space allocated to luggage carts that WN can secure. Since the 5:00 flight was cancelled, the 8:08 flight was the only FL left and they made an exception.
Was very nice that the boys checked three bags free each.
Some days timing is everything.