Entities affiliated with private equity firm Indigo Partners, one of Spirit Airlines' largest shareholders, are selling their shares in the company.
The Miramar, Florida-based airline announces that 12.1 million shares of Spirit's common stock owned by Indigo's affiliates will be made available through a public offering.
"Upon completion of the offering, investment funds affiliated with Indigo will no longer own shares of common stock of Spirit Airlines," the airline says.
Barclays Capital is underwriting the offering.
Spirit's announcement comes just days after Republic Airways Holdings announced it has entered into a "non-binding" agreement to sell subsidiary Frontier Airlines.
In recent months, reports have surfaced that Phoenix-based Indigo and another firm, New York-based Anchorage Capital Group, were interested in buying Denver-based Frontier for between $20 million and $50 million.
Just last week, Michael Boyd, chairman of aviation consulting firm Boyd Group International, told the Denver Business Journal that most industry observers have "long believed Indigo would be the buyer".
He added that Anchorage Capital is not rumoured to be very interested in Frontier.
Spirit also announces today that two of Spirit's board members - chairman William Franke and director John Wilson - will resign 7 August from the board.
Franke, chairman since 2006, is managing partner at Indigo, and Wilson is a principal at Indigo, according to Spirit's website.
The airline says it intends to elect current board member McIntyre Gardner as the new chairman.
The 12.1 million shares owned by Indigo's affiliates equaled 16.6% of Spirit's outstanding stock as of February 2013, says Spirit's 2012 annual report.
That ownership interest allowed Indigo to "exert a significant degree of influence or actual control over our management and affairs and over matters requiring stockholder approval," Spirit says in the report.
Indigo had particular influence over nomination and election of directors, mergers, consolidations and sale of company assets, Spirit says.
Neither Spirit or Indigo could immediately be reached for comment.