A sustained first inflation (SI) at birth may aid lung liquid clearance and aeration, but the impact of SI duration relative to the volume-response of the lung is poorly understood. We compared three SI strategies; 1) variable duration defined by attaining volume equilibrium using real-time electrical impedance tomography (EIT; SI_plat), 2) 30s beyond equilibrium (SI_long) and 3) short 30s SI (SI₃₀) and 4) positive pressure ventilation without SI (no-SI) on spatio-temporal aeration and ventilation (EIT), gas exchange, lung mechanics and regional early markers of injury in preterm lambs. Fifty-nine fetal-instrumented lambs were ventilated for 60 min after applying the allocated first inflation strategy. At study completion molecular and histological markers of lung injury were analysed. The time to SI volume equilibrium, and resultant volume, were highly variable; mean (SD) 55 (34)s, coefficient of variability 59%. SI_plat and SI_long resulted in better lung mechanics, gas exchange and lower ventilator settings than both no-SI and SI₃₀. At 60 min, alveolar-arterial difference in oxygen was a mean (95% CI) 130 (13, 249) higher in SI₃₀ versus SI_long group (2-way ANOVA). These differences were due to better spatio-temporal aeration and tidal ventilation, although all groups showed redistribution of aeration towards the non-dependent lung by 60 min. Histological lung injury scores mirrored spatio-temporal change in aeration and were greatest in SI₃₀ group (p<0.01, Kruskal-Wallis test). An individualized volume-response approach to SI was effective in optimizing aeration, homogeneous tidal ventilation and respiratory outcomes, whilst an inadequate SI duration had no benefit over positive pressure ventilation alone.