Dynamics of the controlled streamer-to-spark transition in atmospheric-pressure air is simulated. Results of calculation show that at proper selection of the parameters (the feeding capacitor, the ballast resistor) of power-supply electric circuit it is possible to produce non-thermal plasma filaments of radii about 10−2 cm, the mean gas temperature inside the filament being about 2000-3000 K and the electron number density being 1013–1014 cm−3.