UPDATE 1-Spirit Airlines rejects JetBlue offer, backs merger with Frontier Group

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June 28 (Reuters) - Spirit Airlines Inc on Tuesday rejected JetBlue Airways Corp's sweetened takeover offer and recommended that shareholders vote in favor of a merger with Frontier Group Holdings Inc at a meeting on Thursday.

JetBlue had on Monday included a ticking fee of 10 cents per Spirit share in its offer, raising the deal value to $34.15 per share, representing a 51% premium to Spirit's Monday closing price.

"The latest offer from JetBlue does nothing to address our Board's serious concerns that a combination with them would not receive regulatory approval," Spirit Chief Executive Ted Christie said in a statement.

Frontier's cash-and-stock offer was valued at $22.03 per share as of Monday's close.

Both JetBlue and Bill Franke-backed Frontier are locked in an intense bidding war for Spirit as they seek to create the fifth-largest airline that can take on the legacy players in the United States.

Shares of JetBlue and Frontier rose more than 3%, while Spirit was up about 2% in early trading amid a broader surge in travel stocks after China eased its quarantine rules. (Reporting by Abhijith Ganapavaram in Bengaluru; Editing by Arun Koyyur)