This is concerning.

management has always said we are "too small" and nobody bothers us blah blah, unfortunately looks like that's changing.

http://m.barrons.com/articles/BL-SWB-39314

By Ben Levisohn
Spirit Airlines (SAVE) provided a dismal second-quarter update today. That’s cratered its own stock but those of other airlines, including Delta Air Lines (DAL), United Continental (UAL), American Airlines (AAL), and JetBlue Airways (JBLU) have remained immune. Cowen’s Helane Becker and team note that “growth for growth’s sake will not be rewarded in this environment,” something Spirit doesn’t appear to have learned yet:

4Q15 Capacity Increase is Baffling…Management is increasing capacity in an environment of weakening prices, which seems aggressive, and we suspect the market will react negatively to this growth. Spirit has long thought of itself as too small to be noticed and too different to matter. The industry has been more aggressive in responding to Spirit’s capacity additions. It will be interesting to see how management responds in 2016 as the expectation is for +20% capacity growth.
Citigroup’s Stephen Trent and Kevin Kaznica cut Spirit to Neutral from Buy:
We reduce our estimates for Spirit Airlines and downgrade the shares from Buy to Neutral. Spirit has enjoyed strong, long-term share price appreciation. However, the shares have also come under pressure this year due to a previous guidance reduction. We believe that Spirit’s weaker, near-term stock price performance at least somewhat protects the carrier from a more negative investment opinion. Our 12M target price for Spirit Airlines declines from $93 to $70/share.
Shares of Spirit Airlines have fallen 8.4% to $58.28 at 11:35 a.m. today, while United Continental has dipped 0.1% to $56.33, Delta Air Lines has risen 0.7% to $43.69, and American Airlines is little changed at $42.43. JetBlue has gained 1.5% to $22.33 after releasing its own traffic update.