A model is proposed for blue jets [Sentman and Wescott, 1995; Wescott et al., 1995a>, which explains their dynamics, in particular the jet vertical velocity of about 100 km/s, the terminal altitudes of about 40--50 km, and the competitive occurrence of blue jets and the recently discovered blue starters [Wescott et al., 1995b>. A blue jet is considered to be formed by an attachment-controlled ionizing wave, which moves upward via an electron avalanche in the wavefront due to the mainly vertical, downward directed quasi-electrostatic field, caused by the extraordinarily large (>100 C) charge transfer in a high-altitude intracloud discharge or in a positive cloud-to-ground discharge with a long continuing current. ¿ American Geophysical Union 1996