Last year, procrastinators were rewarded when they finally got around to booking flights for holiday travel. Back then, airlines were not prepared for the sharp falloff in travel and offered last-minute deals to fill up empty planes. This year? Dilly-dallying, even waiting just a few days, could carry a steep price. Fares, though still lower now than at this time last year, are rising each day, a trajectory that began more than a month ago.