The Florida-based ultra-low-cost carrier is facing a hostile takeover bid by JetBlue Airlines. The company has urged its shareholders to reject JetBlue's offer and back its deal with Frontier.
Spirit will hold a shareholder meeting on June 10 to vote on the transaction with Frontier.
"The vote that we will be soliciting from our shareholders on the 10th is a vote for the Frontier merger," Christie said on an analyst call.
He, however, said Spirit intended to remain a stand-alone entity if shareholders rejected the deal.
(Reporting by Rajesh Kumar Singh; Editing by Leslie Adler and Stephen Coates)