Frontier and Spirit announced plans to merge in February, only for JetBlue to make an all-cash bid in April. The Spirit board has repeatedly rejected JetBlue’s offers.

Spirit shareholders had been due to meet on Thursday (30 June) to discuss the Frontier bid, but the airline’s board will now reconvene on 8 July. It is the second time the meeting has been postponed.

Frontier is considered to be the frontrunner to reach an agreement, with Spirit chief executive Ted Christie still advising Spirit’s shareholders to back its proposal over JetBlue’s.

However, the pause will allow talks to continue between Spirit and its suitors, and give Spirit shareholders more time to give both bids further consideration.

"Spirit Airlines today announced it intends to open and immediately adjourn its special meeting of stockholders relating to the proposed merger agreement with Frontier Group Holdings, parent company of Frontier Airlines, to allow the Spirit board of directors to continue discussions with Frontier and JetBlue Airways Corporation," said Spirit in a statement.

"There will be no voting or other matters conducted at the meeting on 30 June and the company intends to reconvene the special meeting on 8 July."

JetBlue chief executive Robin Hayes said he looked forward to entering into further "constructive and substantive dialogue" with the Spirit board. "It’s clear Spirit shareholders have now handed the Spirit board an undeniable mandate to reach an agreement with JetBlue," he said.

"A combined JetBlue-Spirit would create a truly compelling national competitor to the legacy carriers and a winning combination for customers, JetBlue crew members and Spirit team members," Hayes added.

Whichever deal goes ahead, the resultant group would become the US’s fifth largest airline.