Aircraft As noted above, aircraft use their wing area as the reference area when computing , while automobiles (and many other objects) use projected frontal area; thus, coefficients are not directly comparable between these classes of vehicles. In the aerospace industry, the drag coefficient is sometimes expressed in drag counts where 1 drag count = 0.0001 of a .Basha, W. A. and Ghaly, W. S., "Drag Prediction in Transitional Flow over Airfoils," Journal of Aircraft, Vol. 44, 2007, p. 824–32.
aircraft as noted above aircraft use their wing area as the reference area when computing  while automobiles (and many other objects) use projected frontal area; thus coefficients are not directly comparable between these classes of vehicles in the aerospace industry the drag coefficient is sometimes expressed in drag counts where 1 drag count = 00001 of a basha w a and ghaly w s "drag prediction in transitional flow over airfoils" journal of aircraft vol 44 2007 p 824–32