Spirit Airlines again puts off a vote on Frontier’s offer as it mulls JetBlue’s.

Spirit Airlines said Thursday that it had again delayed a shareholder vote on its proposed acquisition by Frontier Airlines, allowing it to continue discussions with Frontier and with JetBlue Airways, which has made a rival bid.

The vote, which was to take place Friday morning, was rescheduled for July 15.

The postponement is the third time in a month that Spirit has pushed back the vote as it has repeatedly spurned JetBlue, arguing that antitrust regulators would probably reject a combination of the two airlines. Instead, Spirit has encouraged shareholders to support the Frontier deal, which it has said has an easier path to regulatory approval.

JetBlue has argued that regulators are likely to scrutinize either deal and could find as much to object to in a combination of Spirit and Frontier, which compete in many markets. JetBlue’s all-cash offer also values Spirit more highly, at about $3.6 billion; Frontier’s stock-and-cash proposal valued the company at about $2.4 billion.

The Biden administration has taken a dim view of large corporate mergers and is expected to be skeptical of either deal, particularly with airlines struggling to overcome episodes of mass flight cancellations. Either combination would create a new fifth-largest U.S. airline, however, which could better compete with the four carriers that dominate the domestic market.

Spirit and Frontier jointly announced their plan in February, with JetBlue offering a competing bid for Spirit weeks later. Because Spirit and Frontier share a low-cost business model, they are a more natural fit, industry analysts say. And by joining forces, the airlines would create a larger budget carrier that could benefit from national scale.

For JetBlue, acquiring Spirit would accelerate its plans for growth, though combining the two operations could prove more difficult.