A model is presented for the onset and development of solar flares which relies on the transformation of energy to kinetic energy in a plasma. A two-dimensional configuration in which plasma counterflows cross magnetic fields of opposite polarities is considered. The flow velocities are assumed to be both subsonic and sub-Alfvenic, and no shock-wave processes are considered. These velocities are taken sufficiently large to generate a relatively strong electric field and to set up a sequence of instabilities, the first of which is explosive in the region of zero magnetic field. As a result, generation of high- energy particles and onset of a strong turbulent electrical resistivity occur. Following this phase, conversion of magnetic energy into thermal and flow energy takes place as a consequence of a tearinglike mode which is set up around the same region.