Who is Guillaumet from Wind, Sand and Stars and what is their importance?

Guillaumet is a pilot who earned Antoine's undying and loyal respect both as a pilot and as a man. There are two stories that demonstrate his value to Antoine. The first is when, before Antoine has flown his first mission, Guillaumet teaches him on his map of all the unmarked dangers and oases, marking things like fields that serve as good places to land and creeks that will crash a plane if landed on. He shows him the homes of friendly residents and becomes to Antoine a sage source of life-saving experience.