including 25 children. we say likely, because u.s. official tells cnn it s 99.9% certain it was a bomb but not 100%. figuring out what happened is critical to preventing the next such attack with concerns of the 1 million people who work behind the secure lines at american airports. cnn s barbara starr live at pentagon. what s the latest? well, jake, russia and egypt sharing little, almost no information, about this situation. but the u.s. is beginning to develop some ideas about what it believes happened to the russian airliner. as the u.s. tries to connect the dots on what happened to the russian airliner, a working theory is emerging inside the u.s. government about the possible makeup of the plot. more than half a dozen u.s. officials in various parts of the administration now believe it likely was a bomb. officials stress, understanding