JetBlue has agreed to buy Spirit Airlines for $3.8 billion in a deal that would create the nation's fifth largest airline if approved by U.S. regulators.

The agreement Thursday comes a day after Spirit's attempt to merge with Frontier Airlines fell apart. Spirit had recommended its shareholders approve a lower offer from Frontier, saying that antitrust regulators are more likely to reject the bid from JetBlue.

JetBlue said Thursday that it would pay $33.50 per share in cash for Spirit, including a prepayment of $2.50 per share in cash payable once Spirit stockholders approve the transaction. There's also a ticking fee of 10 cents per month starting in January 2023 through closing.

The combined airline would have a fleet of 458 aircraft. The airlines will continue to operate independently until after the transaction closes.