En-route airspace refers to the portion of airspace where aircraft travel between departure and arrival airports. This airspace is typically managed by air traffic control to ensure safe and efficient flight operations. It includes various altitudes and routes that pilots must follow during their journey. In many countries, en-route airspace is divided into different classes, such as Class A, Class B, and Class C, each with specific rules and requirements. These classifications help regulate the flow of air traffic and maintain safety standards. Pilots must be aware of these regulations to navigate through en-route airspace effectively.