When an airplane flies so light on passengers (and their luggage), passengers are either moved around the cabin or extra ballast is added to the baggage hold to make sure it all balances out. Airplanes function like a giant seesaw. By design, the center of gravity of the aircraft is near the main landing gear.

An airplane being "too light" is a rare but critical situation that can significantly affect its Center of Gravity (CG) and aerodynamic performance. Every aircraft has a "Minimum Flight Weight" required to ensure stability. If a plane is significantly underloaded—for example, a large ferry flight with no passengers or cargo—the nose may become too heavy or the tail too light, making the aircraft difficult to "trim" or control during takeoff and landing. In extreme cases of an "aft" (rear) CG imbalance, the plane could tip onto its tail while parked or experience a dangerous pitch-up during the initial climb, potentially leading to a stall. To rectify this, pilots and ground crews use ballast—heavy weights like sandbags or water tanks—placed in specific cargo holds to bring the aircraft within its certified weight and balance "envelope." Additionally, being too light can result in "over-performance" where the engines produce more thrust than the light airframe can safely handle at certain speeds, requiring the pilots to use reduced "de-rated" thrust settings to prevent overstressing the aircraft's structure during the departure.