An airplane has a mass of 1.60-10^4 kg and each wing has an area of 40.0m^2. During level flight, the pressure on the lower wing surface is 7.00-10^4 Pa. Determine the LIFT FORCE on the plane. Is it sufficient to lift the plane? part is what concerns me: if it is in level flight, the net force is zero How do I go about answering this question... leading me in the right direction would be very helpful =) Big thanks!