Key TakeawaysJetBlue and Spirit Airlines have terminated a proposed $3.8 billion merger.The merger would have created the fifth-largest domestic carrier, attracting antitrust scrutiny.JetBlue will pay $69 million in termination fees to Spirit.Both companies will now pursue plans to improve profitability, but there are concerns over Spirit's financial condition. JetBlue (JBLU) and Spirit Airlines (SAVE) have called off their $3.8 billion proposed merger after regulators blocked the deal. Spirit Airlines stoc ...