Spirit Airlines, the target of a budget airline bidding war, is postponing a Friday shareholder vote on whether to accept one of those buyout offers after a flurry of counter proposals from JetBlue and Frontier Airlines. The Miramar, Florida, carrier had scheduled a special shareholders meeting at the end of the week asking investors to sign off on what has been its preferred offer, from Colorado's Frontier Airlines. JetBlue has offered more money than Frontier, but Spirit has rejected those bids saying that any such tie-up would faces a greater likelihood of being shot down by federal regulators.