Who do they believe that they saw in Lord of the Flies?

Samneric in the flickering light of the signal fire see the dead body of an airman, which appears to move as wind blows against the parachute which is still attached to it. They think that they see the beast and in their frightened and confused state the movement of the parachute suggests wings. Later Ralph, Roger and Jack also see the dead body on the mountain top, in the failing light of evening, and reach the same conclusion, that they have also seen the beast.