The ultra-low-cost model is being tested by high fuel costs and shifting consumer preferences toward premium experiences.

One of the last remaining low-cost players, though its ability to capture Spirit's market share is uncertain.

Under pressure as the cost to operate no longer allows for the 'dirt cheap' fares that define the brand's competitive advantage.

Following a 50% price spike, a wave of selling has come from 5 insiders (including the CEO) who have an excellent track record of timing sales, representing a strong bearish signal.

The CEO made a significant unscheduled sale after a 50% rally; historically, the stock has fallen an average of 40% in the three months following his sales.

The CEO sold $3.55 million in an unscheduled sale after a 50% stock run-up. The CEO's previous sales have preceded an average 40% drop, and other insiders are also selling.