Assuming a small relative airfoil thickness and small ratio of densities on incident shock wave front, irregular reflection of a strong shock wave from a curved wall is investigated. The reflected wave is assumed to be small and adjoint to the airfoil edge with an angular zone present at the triple point. The problem is reduced to an integral differential equations system for the front of diffracted shock waves and quadratures. In the self-modeling case with a strong shock wave reflected from a wedge, the problem is reduced to integrating an ordinary differential equation to determine the Mach wave front.