A mathematical analysis has been made of the breakup of liquid drops in an air stream; only the mechanism in which the drops flatten, become bowl‐shaped, inflate like a parachute, and finally burst is considered. The analysis provides an understanding of this process of breakup and the conditions for which the viscosity and surface tension become important factors. An estimate of the breakup time for a wide range of conditions is obtained as a function of the drop diameter, surface tension, viscosity, drop density, air density, and velocity difference. The results are compared with the available experimental data.