FL180, or Flight Level 180, refers to an altitude of 18,000 feet above sea level. In aviation, flight levels are used to standardize altitude reporting, especially in controlled airspace. At this altitude, aircraft typically transition from flying under visual flight rules (VFR) to instrument flight rules (IFR), which allows for safer navigation in poor weather conditions. At FL180, aircraft are often required to maintain a specific vertical separation from one another to prevent collisions. This altitude is significant for commercial airlines and private pilots alike, as it marks the beginning of the upper airspace where air traffic control manages flights more closely, ensuring efficient and safe travel.