The interplay between an applied electric field and fluid properties was studied for a polymer solution forming high quality nanofibers via electrospinning. Unconfined electrospinning-in which a fluid thin film or bath exposed to an electric field spontaneously generates many parallel fiber-forming jets-is a practical approach to achieving a high fabrication rate of quality nanofibers as compared to traditional single-needle electrospinning. The density of fiber-forming jets is controlled by surface tension effects at the lowest applied voltages but by jet-to-jet. interactions as the voltage amplitude is increased, resulting in an intermediate operating voltage level at which jet number is maximized. This general result is applicable to electric-field-driven fluid instabilities in a wide range of systems. The optimal voltage level occurs when interjet interactions begin to solely determine the characteristic jet spacing, and in this regime, compression of the cone-jet slightly chokes the feed rate, allowing high quality fibers to be formed when the maximum number of jets is present. Spontaneous jet deflection (here, from a linearly arranged source) results in a two-dimensional array at the collector which both minimizes interjet interactions and preserves fiber quality.