"While we are disappointed that Spirit Airlines shareholders failed to recognize the value and consumer potential inherent in our proposed combination, the Frontier Board took a disciplined approach throughout the course of its negotiations with Spirit," said Frontier CEO William Franke. "As we enter our next chapter, Frontier remains well-positioned to deliver significant value to our shareholders as we serve the growing demand for affordable air travel."

A combination of Spirit and Frontier would have brought together two airlines that have very low base fares, but charge passengers extra for most things, including carry-on bags.

Spirit had by far the highest number of passenger complaints in 2021, with 11.45 complaints per 100,000 passengers, according to the US Department of Transportation. JetBlue had the second most complaints on that basis with 6.38, while Frontier came in third with 5.78. Frontier had by far the worst rate of complaints in 2020, when it recorded 49.31 complaints per 100,000 customers.

JetBlue said it expects to move forward with its effort to buy Spirit.