Inviscid and turbulent airflows over a symmetric flat-sided double wedge are studied numerically. Solutions of the Euler and Navier-Stokes equations are obtained with a finite-volume solver on fine meshes. The solutions demonstrate both symmetric and asymmetric flow regimes in significant bands of the free-stream Mach number at zero angle of attack. The realization of a certain regime depends on the time history of boundary conditions. A physical interpretation of transitions between the symmetric and asymmetric flows is suggested.