that aircraft can always find a suitable runway. Almost all runways are reversible, and aircraft use whichever runway in whichever direction is best suited to the wind. In light and variable wind conditions, the direction of the runway in use might change several times during the day. Layout Traffic patterns can be defined as left-hand or right-hand according to which way the turns in the pattern are performed. They are usually left-hand turns because most small airplanes are piloted from the left seat (or the senior pilot or pilot-in-command sits in the left seat), and so the pilot has better visibility out the left window. Right-hand patterns will be set up for parallel runways, for noise abatement, or because of ground features (such as terrain, towers, etc.). In the US, the non-standard (i.e. right-hand) patterns are noted in the Airport/Facilities Directory or on a sectional chart; in other countries they may be indicated in that nation's similar document, e.g. Canada Flight Supplement. Unless explicitly indicated otherwise, all traffic patterns at non-towered airports are to the left. The direction of the pattern may be indicated by a traffic pattern indicator in the aerodrome's signal square. In the United States, the Code of Federal Regulations CFR 91.126 a. (2) requires helicopters to avoid the flow of fixed wing aircraft. Because the active runway is chosen to meet the wind at the nearest angle (with take-offs and landings upwind), the pattern orientation also depends on wind direction. Patterns are typically rectangular in basic shape, and include the runway along one long side of the rectangle. Each leg of the pattern has a particular name: Upwind leg. A flight path parallel to and in the direction of the landing runway. It is offset from the runway and opposite the downwind leg. Crosswind leg. A short climbing flight path at right angles to the departure end of the runway. Downwind leg. A long level flight path parallel to but in the opposite direction of the landing runway. (Some consider it to have "sub-legs" of early, mid and late. Certainly a plane giving a position report of "mid-downwind" can be visually located easily.) Base leg. A short descending flight path at right angles to the approach end extended centerline of the landing runway. Final approach. A descending flight path in the direction of landing along the extended runway centerline from the base leg to the runway.