>> good morning, i'm marci gonzalez in for diana perez. >> and i'm john muller. we start this morning with homeland security officials issuing a warning to airlines about a dangerous new terrorist threat, one that will sound very familiar. >> they say airport security screeners should be on the lookout for shoes used to smuggle explosives on to commercial jets. here is abc's pierre thomas. >> reporter: homeland security officials are warning airline that is explosives hidden in shoes and other improvised bombs are an active ongoing threat. abc news learns that terrorists are building shoe bombs with liquid explosives, hidden in containers to target international flights. no plot has been identified but intelligence from credible overseas sources suggest that terrorist bomb makers are fixated on these efforts. >> it certainly tells you that