What happens while the boys are sleeping in the shelter?

In Chapter Six,  Ralph and Simon pick up Percival and carry him into a shelter. Overhead, beyond the horizon, there is an aerial battle while the boys sleep. They do not hear the explosions in the sky, nor do they see a pilot drop from a parachute, sweeping across the reef toward the mountain. Unbeknownst to the boys, the dead pilot lands on the mountaintop, his flapping chute throwing strange shadows across the ground, with his head appearing to float in the wind.