Yes it would. Each sea gull weighs two pounds, that means gravity is pulling down on each seagull with a force of two pounds. In order to stay flying, the seagulls have to exert a downward force equal to that of the gravitational force. The force of gravity and the downward force of the seagulls would cancel out.. The downward force exerted by the seagulls ends up being exerted against the floor of the plane, causing the plane to weigh 2000 pounds more.