Spirit Airlines said it received an "unsolicited proposal" from JetBlue to purchase all outstanding shares of Spirit's stock for $33 per share.
"The Spirit Board of Directors will work with its financial and legal advisors to evaluate JetBlue's proposal and pursue the course of action it determines to be in the best interests of Spirit and its stockholders," the airline said in a statement.
The offer could roil plans by Frontier Airlines to merge with Spirit, which would create the nation's fifth-largest carrier.
JetBlue argued Tuesday that their acquisition of Spirit would lead to a "customer-centric, low-fare alternative to the dominant 'Big Four' airlines."
"Customers shouldn’t have to choose between a low fare and a great experience, and JetBlue has shown it’s possible to have both," JetBlue CEO Robin Hayes said in a statement.
"The combination of JetBlue and Spirit – coupled with the incredible benefits of our Northeast Alliance with American Airlines – would be a game changer in our ability to deliver superior value on a national scale to customers, crewmembers, communities, and shareholders."
A spokesperson for Frontier Airlines contested that their merger with Spirit would lead to "even more ultra-low fares to more places nationwide" and "provide both Spirit and Frontier shareholders with substantial upside potential."
"Unlike the compelling Spirit-Frontier combination, an acquisition of Spirit by JetBlue, a high-fare carrier, would lead to more expensive travel for consumers," a Frontier spokesperson told Fox Business. "In particular, the significant East Coast overlap between JetBlue and Spirit would reduce competition and limit options for consumers.
Shares of Spirit Airlines stock jumped 28% on Tuesday afternoon to about $26.91 a share after the news came out.
JetBlue's stock closed down about 6.5%.
The potential bidding war comes as airlines try to get back on their feet following two years of reduced business due to the coronavirus pandemic.