Which factor contributes to longer takeoff distances in heavier fuel loads?

In the context of takeoff distances and heavy fuel loads, the factor that significantly contributes is decreased thrust. When an aircraft has a heavier fuel load, it results in an increase in the overall weight of the aircraft. While the engines may still produce thrust, the increase in weight requires more power to achieve the necessary speed for takeoff.

Heavier aircraft often need a longer distance to reach the required speed for liftoff due to the increased inertia. Additionally, if the engines are not capable of producing sufficient thrust relative to the increased weight, this will further extend the takeoff distance as the aircraft struggles to reach the necessary airspeed.

In summary, heavier loads create a situation where the required thrust to overcome the inertia and get the aircraft airborne is greater, thus contributing to longer takeoff distances.