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 Frontier Airlines and JetBlue.

The decision to postpone a vote comes two days after JetBlue improved its offer. Spirit said Wednesday that has rescheduled the vote for June 30, giving its board another three weeks to speak with Frontier, JetBlue, as well as its own shareholders.

The Miramar, Florida, carrier had scheduled a special shareholders meeting at the end of the and had been 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 face a greater likelihood of being shot down by federal regulators.

The bidding war for Spirit has heated up in the past few days, with JetBlue attempting to allay concerns that the U.S. would block its acquisition.

The New York airline on Monday offered a $350 million reverse break-up fee payable to Spirit if a deal between the two isn't completed for antitrust reasons, topping its previous contingency plan by $150 million.

Last month, JetBlue went hostile in its attempt to buy Spirit, taking its offer directly to shareholders of the airline. Spirit CEO Ted Christie has said that JetBlue is more interested in breaking up a deal with Frontier than it is in owning Spirit.

Shares of Frontier dipped 3%, JetBlue 2% and Spirit less than 1% Wednesday.