In aviation, the Maximum Take-Off Weight (or MTOW) is the maximum weight with which an aircraft can achieve flight. MTOW is affected by the design of the airframe, engine type and power, drive type (e.g. fixed propellor vs. turbofan), and air density. MTOW calculations are all-inclusive, representing the sum of the weights of the airframe, fuel, cargo, and personnel.

An airplane's rated MTOW and other performance ratings are based on the International Civil Aviation Organization's International Standard Atmosphere (or ISA).

However, real world conditions often differ from the ISA. Air density is dependent on the altitude of the runway, barometric pressure, and air temperature. Increases in runway altitude, decreases in barometric pressure, and increases in air temperature each cause a decrease in an aircraft's effective MTOW for the conditions.