Complex sentence: The French Sector existed as a stipulation of an agreement between France and the Canton of Geneva dating from the 1960s, and enabled travel between the neighboring French region of the Pays de Gex and the airport while avoiding Swiss territory and customs.
Split into simpler sentences: The French Sector exists as a stipulation of an agreement between France and the Canton of Geneva dating from the 1960s. This sector enables travel between the neighboring French region of the Pays de Gex and the airport, avoiding Swiss territory and customs.