Purpose <p>Risk factors that classify patients with postoperative air leaks into prolonged-air-leak (PAL, ≥ 5 days) and non-PAL populations remain unknown. Our objectives were to identify these risk factors and devise a scoring system to predict whether air leaks observed on postoperative day 1 will progress to PAL.</p> Methods <p>We conducted a retrospective examination of 329 patients after lung surgery.</p> Results <p>Significant factors associated with air leaks included male sex (<i>p</i> = 0.0097), low body mass index (BMI) (<i>p</i> = 0.0016), smoking (<i>p</i> = 0.0076), pack-years (0.0017), predicted vital capacity (<i>p</i> = 0.0053), predicted forced expiratory volume in one second (<i>p</i> = 0.0352), and operative duration (<i>p</i> = 0.0118). Furthermore, in patients with air leaks on the day after surgery, significant factors associated with PAL included low BMI (<i>p</i> = 0.0248), current smoking (<i>p</i> = 0.0054), pack-years (<i>p</i> = 0.005), and significant blood loss (<i>p</i> = 0.0147). Upon classifying the patients on day 1, one point each was allotted for BMI &lt; 23.7, pack-years ≥ 28.5, current smoker, and blood loss ≥ 38&#xa0;ml. Depending upon the risk factors present, the rates of PAL observed were 0%, 7.69%, 33.33%, 70.59%, and 83.33% associated with 0, 1, 2, 3, and 4 points, respectively (<i>p</i> &lt; 0.001).</p> Conclusions <p>For the first time, we identified risk factors for the onset of postoperative air leakage and PAL.</p>