What does MSL stand for?

MSL stands for Mean Sea Level, which is a standard reference used in aviation and various fields to measure altitude. It represents the average height of the sea's surface over a long period and is used as a baseline for altitude measurements. Understanding MSL is crucial for pilots and drone operators, as it helps them maintain safe flying altitudes relative to the Earth's surface and avoids potential obstacles, such as mountains or buildings, ensuring compliance with regulations and enhancing safety during flight operations. The other definitions provided in the choices do not correspond to a commonly recognized term used in aviation or navigational contexts, making Mean Sea Level the correct and relevant choice here.