CHICAGO--(BUSINESS WIRE)--Fitch Ratings has made public an Issuer Default Rating (IDR) of 'BB+' for Spirit Airlines. The Rating Outlook is Stable. KEY RATING DRIVERS The rating is supported by Spirit's industry-leading operating margins, healthy liquidity, low cost structure, and modest leverage. Fitch believes that Spirit's cost advantage over its peers gives the company significant cushion to operate through potential future economic downturns while maintaining adequate financial health. The