Shares of Spirit Airlines gained 3 percent after Credit Suisse upgraded the company to "outperform."
The firm also increased its price target to $55 from $44, implying a 25 percent upside to the stock's Monday closing price of $43.85.
In Credit Suisse's note, the firm said it expects Spirit's earnings to grow by 15 percent in 2017 despite higher fuel costs, "which is unique among [its] coverage."
The firm also cited Spirit CEO Robert Fornaro's investment in operations will pay off.
"Improved operational performance should result in better load factors for [Spirit Airlines] over time and is a natural evolution of the model to improve the brand and take greater share from legacy carriers (the same way Ryanair has in the EU)," the firm said in its note.