Aircraft fly when they generate more lift than drag. You can calculate lift using the aircraft's velocity, its wings' surface area and the density of air.

Square the aircraft's velocity. For instance, if it's traveling at 60 meters per second:

60 * 60 = 3,600

Multiply your answer by the density of air. For instance, if the density is 1.2 kilograms per cubic meter:

3,600 * 1.2 = 4,320

Multiply by the combined upper surface area of both wings. If the surface area is 30 square meters:

4,320 * 30 = 129,600

Divide by 2.

129,600 / 2

\= 64,800

Multiply by the lift coefficient. If your lift coefficient is 0.2:

64,800 * 0.2 = 12,960 newtons.

A newton is the force required to accelerate a kilogram 1 meter per second per second.