The Last Adventure aka Les aventuriers (All Region DVD) 1967 Alain Delon, Lino Ventura, Joanna Shimkus

Two best friends, Roland and Manu, are the victims of a practical joke that costs Manu his pilot's license. But soon they are off on a treasure hunt.
Director: Robert Enrico
HALF MEASURES: This movie only used the first half of the novel by José Giovanni. The second half of the book was adapted into the film Law of Survival (1967) (La loi du survivant) starring Michel Constantin, directed by Giovanni himself.