Being told a flight is "weight restricted" is frustrating, especially when you can see empty seats on the plane. But this is a fundamental safety limit dictated by physics and the Maximum Takeoff Weight (MTOW).

The Takeoff Equation

An aircraft's weight consists of the Empty Weight, Payload (passengers/bags), and Fuel. If the combination of these exceeds the MTOW-which is lower at high-altitude airports or in extreme heat-the airline must reduce payload. Because fuel is non-negotiable for safety, bags and passengers are the only things that can be removed to stay within legal limits.