The setting of William Golding's Lord of the Flies is a tropical island; the characters are English schoolboys who were on an airplane which was evacuating them during World War II. Golding is not especially forthcoming about the particulars of the crash which deposits the boys on the island, but several deductions can be made about the crash and the whereabouts of the wrecked aircraft.
First, the airplane was low enough to leave a "scar" in the island jungle. In fact, the first description of the island includes a reference to it: "the long scar smashed into the jungle." Later Piggy notes that the scar was made by the cabin of the plane. This is undoubtedly why the boys are able to survive the crash.
Second, none of the adults survived. There was a pilot and a "man with a megaphone" shouting orders to the boys in the passenger cabin, but neither of them survived. Piggy recalls looking out of the plane's window and seeing flames coming from what must have been the wing. Despite that, the cabin cut through the jungle and the boys survived.
Finally, the aircraft must have been dragged to sea in the storm. “What happened to it?” [Ralph] asked. “Where’s it got to now?” Piggy answered:
“That storm dragged it out to sea. It wasn’t half dangerous with all them tree trunks falling. There must have been some kids still in it.”
Of course we learn that all of the boys survived, but this is the best explanation we get about where the actual airplane went after the crash.
Readers are often frustrated not to have at least a little more information about how, specifically, the plane deposited the boys on the island and what happened to it afterward; however, Golding clearly did not think that was a particularly important aspect of the story or he would have given us more detail.