Spirit said its board unanimously determined the JetBlue proposal is not in the best interests of the carrier or its shareholders. The potential transaction “faces substantial regulatory hurdles” and is unlikely to be successfully completed, Spirit said Thursday in a statement. Spirit again recommended shareholders vote in favor of Frontier’s bid.

It was the second rejection of a JetBlue bid by Spirit’s board, which stood by Frontier’s $2.9 billion cash-and-stock deal agreed to in February. After an unsuccessful $3.6 billion cash offer, JetBlue on May 16 went hostile, offering the reduced proposal directly to Spirit shareholders in a tender offer.

Spirit shareholders will decide the issue during a June 10 special meeting.

JetBlue fired back at Spirit, accusing its board of ignoring the best interests of shareholders and refusing to negotiate in good faith. “Spirit would have you ignore the current regulatory climate to think that approval of their Frontier deal is assured. That is simply not true,” it said in a statement. “Both deals are subject to regulatory review, and both deals have a similar risk profile.”

Frontier didn’t immediately respond to a request for comment. 

The no-frills carrier stuck by its earlier reasoning that the Frontier offer has a better chance of closing. Market overlap in the eastern U.S. between JetBlue and Spirit could raise antitrust questions at the same time JetBlue battles a federal lawsuit over a business alliance with American Airlines Group Inc. 

Spirit shares fell 2.8% to $18.87 as of 8:53 a.m. before regular trading in New York. Frontier dropped 3.4%,  while JetBlue slipped 1.2%.

JetBlue seeks growth

With the pursuit of Spirit, JetBlue is seeking a burst of growth it can’t otherwise attain. The rival bid by Frontier would combine similarly focused deep-discounter carriers offering bare-bones low fares while charging for extras like coffee, bottled water and printed boarding passes. Either combination would pass Alaska Air Group Inc. to become the fifth-largest U.S. airline by capacity.

Spirit’s allure stems in part from an industrywide turn toward domestic markets and leisure travelers—the bread-and-butter of ultra-low-cost airlines—as it’s recovered from a pandemic slump. Bigger carriers have moved more heavily onto that turf amid the slow return of overseas travel demand.

Under the Frontier deal, investors in Miramar, Florida-based Spirit would receive 1.9126 in Frontier stock and $2.13 in cash for each Spirit share. The deal implies a value of $25.83 a share for Spirit. Assumption of net debt and operating lease liabilities push the total value to $6.6 billion. Holders of Denver-based Frontier would own 51.5% of the combined company and name seven of the twelve directors. The agreement includes a $94.2 million breakup fee.

JetBlue has said its offer isn’t subject to approval by its shareholders or to a financing contingency, and includes a $200 million “reverse breakup fee” payable to Spirit if a deal is blocked for antitrust reasons. The proposed deal would generate as much as $700 million in annual synergies, the carrier has said.

A Spirit deal would give JetBlue, hounded by Wall Street analysts for much of its 23-year history over cost creep, access to an organization and management team highly focused on keeping operating expenses in check. JetBlue lost out in its only other takeover attempt when it was outbid by Alaska for Virgin America in 2016.

—With assistance from Justin Bachman.