IOWs, nothing conclusive here! Looking for actual accidents, not   

6. Conclusion There is a discernible pattern of increased probability of an accident the greater the hours of duty time for commercial aircraft pilots in the United States. Although the empirical analysis reported above notes that pilot scheduling was not a factor in all of these accidents, it does point to increased risk of accidents with increased duty time and cumulative duty time. The analysis does not indicate any discontinuity at a specific duty time such that it would point to exactly where risk increases significantly. Rather, the data show a relatively constant increase with increased length of work periods. In light of the above, the analysis suggests that establishing limits on duty time for commercial pilots would reduce risk.