What happened

Shares of Spirit Airlines (SAVE 1.30%) are up 15.1% as of 12:46 p.m. EST after the company published new guidance for its fiscal fourth quarter in an 8-K filing with the SEC last night.

Although Spirit's guidance is "preliminary" at this point in time, things appear to be looking up for the discount airline. Total revenue per available seat mile (TRASM), which Spirit had expected would grow 6% year over year, now looks to be coming in closer to 11% -- twice the rate of growth experienced in Q3

Spirit Airlines airplane in yellow and black livery

Image source: Spirit Airlines.

So what

Spirit says its improved revenue was "primarily driven by higher non-ticket revenue and higher load factor expectations," and in particular, by company initiatives to "dynamically price non-ticket items such as seats, bags, and bundled service offerings."

As regards the improved load factors (i.e., filling more seats with paying passengers in each plane that takes off), Spirit credits its "recent network realignment, as well as its move to optimize peak and off-peak scheduling."

And in general, management says that "a stronger industry environment, particularly around peak travel periods, is also contributing some portion of the improved revenue outlook."

Now what

Spirit did not give new specific revenue and earnings guidance for Q4. That being said, with analysts forecasting 22.7% sales growth in the quarter, but available seat miles (ASMs) growing 15% and total revenue per that growing number of ASMs increasing 11%, the combined effect looks likely to add up to better than 22.7% sales growth -- and to produce at least a sales beat for Spirit when Q4 earnings come out.

No wonder shareholders are cheering.