Spirit Airlines shares plunged Wednesday on a report that the budget carrier is getting ready to file for bankruptcy protection after revived merger talks with Frontier Airlines parent Frontier Group Holdings collapsed.

The budget carrier is in advanced discussions with bondholders over a filing that could occur within weeks. In a bold projection that's sure to grab attention, veteran Wall Street strategist Ed Yardeni is calling for the S&P 500 index to soar to 10,

Spirit Airlines is on the brink of filing for Chapter 11 bankruptcy protection following the collapse of its merger talks with Frontier Airlines. With more than $3 billion in debt, Spirit is negotiating with bondholders for a restructuring plan that could allow it to continue operations under bankruptcy protection.