In Chapter 1 of Lord of the Flies, what had Piggy overheard the pilot saying?
In the novel Lord of the Flies by William Golding, the author has Piggy tell Ralph some news that Ralph does not know. This news (about a "they" who have all died, and an "atom bomb") is one of the first signs of Piggy's superiority over Ralph (and some of the other boys) in terms of the clarity of his inner "vision." This of course, is symbolized by the life-saving properties of his spectacles which are needed for fire-lighting. Piggy is obviously a "dark horse" - a character whose wisdom and capabilities, observation and news awareness, belie his appearance, unlike Jack whose angelic choirboy outfit hides something much darker. The curious thing is that, actually, "they" cannot mean everyone - the naval officer is obviously not one of them as he is alive. It is possible that Piggy meant the Japanese navy, or some other enemy.
In Chapter 1, the boys have just been stranded on the island when the plane they were riding in crashed. While they were in the plane, Piggy heard the pilot say something about an atom bomb. He tells Ralph that "they're all dead."
Piggy tells Ralph this because Ralph is talking about how his dad is in the Navy and will come rescue them. Piggy asks him how his dad will know they've crashed. Ralph says the people at the airport would have told him. This is when Piggy says that (from what the pilot said) they are all dead.
It's not completely clear who "they" are -- Piggy believes Ralph's dad is alive, but not the people at the airport who could tell him what happened.