If air density increases while the airspeed remains the same, which statement best describes lift and drag?

• A. Both decrease
• B. Lift increases, drag decreases
• C. Both increase
• D. Lift decreases, drag increases

Answer: (C)

Lift and drag both increase with air density at a fixed airspeed because these forces depend on dynamic pressure, which grows as density rises. Lift is proportional to rho times V^2 times wing area and lift coefficient, while drag is proportional to the same dynamic pressure times area and drag coefficient. With velocity and wing geometry held constant, increasing density directly increases both lift and drag in proportion to rho. So at the same speed, denser air gives more lift and more drag. This explains why lower altitudes (denser air) improve takeoff lift but also raise drag, impacting performance.