Shares of JetBlue Airways jumped Tuesday after activist investor Carl Icahn bought a nearly 10% stake in the carrier.   The billionaire behind Icahn Enterprises owns 33.62 million shares, which is equivalent to a 9.91% stake, according to a filing with the Securities and Exchange Commission which also noted Icahn believes the shares are "undervalued and represented an attractive investment opportunity."Ticker Security Last Change Change % JBLU JETBLUE AIRWAYS CORP. 6.07 +0.13 +2.19% JetBlue's stock is on p ...