who can put bombs on to planes that can't be detected. >> reporter: that bomb maker, ibrahim al asiri, is bleached to be responsible for several attempts against the u.s., including the failed 2009 christmas day underwear bomber attack. he is not seen in the video, which eamerican emerged on jihadist websites. intelligence experts say he and other aqap leaders have gone back to using couriers to communicate to avoid detection, making it even harder to figure out what wahishi may be up to next. >> and his message to the united states was very much the same as bin laden's, we're coming after you. >> reporter: and that man, ibrahim al asiri, the master bomb maker for al qaeda in yemen, he's the one man not seen in this video. the u.s. very much believes he remains in hiding, and there is a great deal of concern about what he may be up to next. don. >> barbara starr, thank you,