In aviation, endurance is the maximum length of time that an aircraft can spend in cruising flight. In other words, it is the amount of time an aircraft can stay in the air with one load of fuel. Endurance is different from range, which is a measure of distance flown. For example, a typical sailplane exhibits high endurance characteristics but poor range characteristics. Endurance can be defined as: where W stands for fuel weight, F for fuel flow, and t for time.