Nanofibres can be processed into several high-end applications due to their unique characteristics, especially when based on a diversity of polymers with specific properties. This, however, requires that the nanofibrous structures are produced in a highly reproducible way. The article gives focus to polyamide (PA) 6.9, a less exploited PA though with interesting properties such as a very low moisture absorption. To trace and understand the dominant parameters that allow for the aimed reproducible characteristics, the influence of the solution parameters on the steady state behaviour during electrospinning as well as the resultant fibre morphology is followed by scanning electron microscopy and differential scanning calorimetry. Results show a significant effect of the amount of non-solvent acetic acid, added to the solvent formic acid, on the steady state behaviour and the fibre morphology. The non-solvent acetic acid broadens the steady state window by making the electrospin solutions more suitable to obtain uniform and reproducible nanofibrous structures with a narrow nanofibre diameter distribution. The mixture of the solvent formic acid and the non-solvent acetic acid strongly contributes to the future potentials of PA 6.9 nanofibres, with its leading to a smaller fibre distribution and moreover highly reproducible in time.