The airline was originally set to vote on the deal on June 10 and the change comes two days after JetBlue Airways Corp improved its buyout offer for Spirit.

Below are the key events in the takeover saga:

Date Development

Feb. 7 Frontier makes a cash-and-stock offer of $25.83/share for Spirit

Airlines

Feb. 8 Lawyers from the U.S. Justice Department say Spirit and Frontier's

merger to create the fifth-largest airline in the country would

face close scrutiny

March 10 Several public advocacy groups call on U.S. regulators to block

Frontier's bid for Spirit

April 5 JetBlue makes an unsolicited $3.6 billion, or $33/share, all-cash

bid for Spirit

April 6 JetBlue mounts a vigorous defense of its unsolicited $3.6 billion

bid for Spirit, adding that it is "highly confident" of securing

regulatory approval

April 7 Spirit says that it would enter into discussions with JetBlue on

its $3.6-billion offer as it could likely lead to a "superior

proposal" to the one from Frontier

May 2 Spirit rejects JetBlue's $33/share offer, saying it had a low

likelihood of winning regulatory approval

May 10 Head of Sun Country Airlines throws his backing behind potential

merger in the ultra-low-cost airline sector

May 11 Spirit says it will hold a shareholder meeting on June 10 for a

vote on its proposed merger with Frontier

May 16 JetBlue makes hostile all-cash takeover offer of $30/share and adds

it was ready to "negotiate in good faith a consensual transaction

at $33"

May 19 Spirit Airlines urges shareholders to reject the hostile offer from

JetBlue, saying it was "a cynical attempt to disrupt" its merger

with Frontier

May 31 Proxy advisory firm ISS urges Spirit shareholders to vote against a

proposed merger with Frontier

June 2 Frontier agrees to pay a break-up fee of $250 million in a bid to

salvage its $2.9 billion acquisition of Spirit Airlines

June 3 Shareholder advisory firm Glass Lewis recommends Spirit Airlines

investors approve Frontier Group's $2.9 billion takeover bid,

saying it was the "best available" at this time.

June 6 JetBlue sweetens its takeover bid for Spirit by offering $31.50 per

share in cash, comprising $30 per share at deal close and the

prepayment of $1.50 per share of the reverse break-up fee.

June 8 Spirit Airlines delays to June 30 a shareholder meeting to vote on

its proposed merger with Frontier.

(Reporting by Nathan Gomes and Kannaki Deka in Bengaluru; Editing by Shounak Dasgupta, Anil D'Silva and Sriraj Kalluvila)