In United States aviation, a sectional chart, often called sectional for short, is a type of aeronautical chart designed for navigation under visual flight rules. In Australia, Canada and some other countries, the equivalent charts used for visual flight are called VFR Navigation Charts (VNCs). The sectionals are complemented by Terminal Area Charts (TACs) at 1:250,000 scale for the areas around major U.S. airports, and World Aeronautical Charts (WACs) at a scale of 1:1,000,000 for pilots of slower aircraft and aircraft at high altitude. The charts are updated at six-month intervals.