JetBlue Airways offered Spirit Airlines $3.6 billion to buy it, all cash. Less than 2 months ago, Spirit and Frontier Airlines agreed to merge. This offer is now raising questions about the merger with Frontier. After finding out about the offer, Spirit said its board was evaluating JetBlue’s proposal, and it will “pursue the course of action it determines to be in the best interests of Spirit and its stockholders.” If Spirit and Frontier merge, they will become the 5th biggest airline in the country. Trading in Spirit shares was stopped before the market closed, after the stock went up over 22%. JetBlue stock closed down 9%.