When is it that Brian decides to try to get into the plane? What does he hope to find? Why hasn't he tried to find it earlier?

Brian waits until he has eaten and regained his strength. He also builds a raft, which he names ‘Brushpile One'. Brian hopes to find emergency supplies and food in the tail of the plane. He did not remember the tail of the plane had these items before. He also did not have the strength to get them.