airports. depending, instead, they be stored in checked luggage. >> elevated intelligence that we're aware terrorist groups target commercial aviation and pursuing methods to undertake their attacks to smuggle explosive device and various consumer objects. >> reporter: officials have told cnn that there was credible and specific intelligence that isis would try to attack aviation assets and a hint from a top u.s. commander on why the accelerated effort on the ground in syria against the group. >> there's an imperative to get isolation in place around roaqq because significant external operation attacks planning. >> reporter: al qaeda's affiliate in yemen has for years been actively trying to target airliners destine for the u.s.