Greg wonders, "What effect if any does seasonal airfare have on us. I notice when booking a recent allegiant trip that sometimes flights are only 2 days a week while other time 4 days a week."
The number of people traveling by air peaks in the summer; trends down through the fall and hits rock bottom in January. Take a look at the graph. This shows the pattern for Springfield in 2007. In January there were 54,438 total passengers. In June: 85,354. December: 69,758.
The January 2008 number will be similar to the same month last year. With few exceptions our graph always looks something like this and the same is true for the industry as a whole. The airlines counter the winter downtime by lowering fares and cutting flights. This is what Greg noticed with Allegiant.
Here's a tip for the savvy air traveler: start looking for the bargain January/February fares in November and December.