CHICAGO--(BUSINESS WIRE)--Fitch Ratings has assigned the following expected ratings to the Spirit Airlines. Inc. (SAVE, rated 'BB+'; Outlook Stable by Fitch) proposed pass through trusts series 2015-1: --$455.6 million class A certificates due in April 2028; 'A(EXP)'; --$121 million class B certificates due in April 2024; 'BBB+(EXP)'. New Issue Report: Fitch will also publish a new issue report, which will be available at www.fitchratings.com. KEY RATING DRIVERS The A-tranche ratings are primar