KEY TAKEAWAYSSpirit Airlines shares are surging in premarket trading Wednesday on a report that Frontier Airlines parent Frontier Group Holdings is in the early stages of a renewed bid for its rival discount carrier.The Wall Street Journal said the two sides have had recent discussions and the deal would form part of Spirit's debt restructuring.Spirit is currently in the midst of discussions with bondholders ahead of a potential bankruptcy filing, the report said, noting that merger talks are in early stage ...