Joe Raedle | Getty Images Shares of Spirit Airlines rose more than 22% on Tuesday after a report that JetBlue Airways had submitted a bid for the financial carrier, raising questions about Spirit’s deal to partner with rival rival Frontier Airlines. Spirit confirmed after the market closed on Tuesday that JetBlue had made an unsolicited offer. The JetBlue offer, previously reported by the New York Times, comes less than two months after Spirit and Frontier agreed to merge into a discount airline. Spirit said its board was evaluating JetBlue’s proposal and would “continue the course of action that it considers to be in the best interests of Spirit and its shareholders.” Competition for Spirit shows a renewed appetite for airline integration as it digs its way out of two difficult years of travel pandemic affecting travel demand. Carriers are now trying to hire to achieve a travel recovery. A wave of consolidation that began more than a decade ago has left four major airlines controlling more than 70% of the US market. Spirit trading stopped before the market closed. Its shares were at $ 26.93. JetBlue offered $ 33 per share in its cash offer, according to Spirit. JetBlue and Frontier did not immediately comment to CNBC. Shares of JetBlue closed down about 7%. Spirit and Frontier both fly exclusively Airbus A320 family aircraft. These make up the majority of JetBlue’s fleet, which will reduce costs and accounting headaches for a combination of carriers. However, JetBlue has a partnership with American Airlines that allows airlines to coordinate services in the northeastern United States. The two airlines said the deal would give them better opportunities to compete with United and Delta Air Lines at busy airports in New York and Boston. The Ministry of Justice sued to block this cooperation last year. The American refused to comment on JetBlue’s offer for Spirit.