As airspeed increases from below Mach 1.0, how does the coefficient of drag behave?

• A. It increases and then decreases
• B. It stays constant
• C. It increases steadily
• D. It decreases then increases

Answer: (A)

As speed rises from well below Mach 1.0, compressibility effects become more pronounced and shock waves begin to form on aircraft surfaces. This creates additional wave drag, causing the drag coefficient to rise as you approach the transonic region. Once you pass through that transonic range, the shock patterns reconfigure and the flow tightens around the body, so the drag coefficient drops somewhat even though speed continues to increase. This combination—drag rising toward a peak near the transonic regime and then decreasing afterward—explains why the best answer is that the coefficient of drag increases and then decreases with increasing airspeed from below Mach 1.0.