Veteran activist investor Carl Icahn's latest involvement in the airline industry deepened on Tuesday. His Icahn Enterprises (IEP 1.51%) successfully installed two of its executives on JetBlue's (JBLU 0.72%) board of directors. That news was encouraging enough to send Icahn Enterprises's stock into positive territory; it closed the day 1.5% higher, in contrast to the 0.6% slump of the S&P 500 index.The veteran activist investor gets active with JetBlueAfter market hours on Friday, JetBlue announced the two ...