OP -
Spirit doesn't pay on advertising; it relies on it's customers and friends (doesn't matter if it's good or bad publicity!). Below is a quote from a WSJ Interview with Spirit's CEO:
"One way to advertise your product is to create good-looking TV ads, radio ads, advertise in newspapers. We don't do any of that.
We email those ads to millions of people. People talk about them, email them to friends, they laugh about them, or get mad about them, or write a blog about how insensitive we are, or how funny we are. We've gotten all of that.
It allows us to spend less money as a percent of our revenue on marketing than any other airline by a long shot. And yet we have huge name recognition across the country—in part because of negative media—but people know we're a low-fare carrier."
You can read the article/interview on WSJ:
http://professional.wsj.com/article/...?mg=reno64-wsj