From the executive summary of "Pilot Age and Accident Rates Report 4. Executive summary:

"The findings are consistent across the three analyses. First, for accidents occurringunder 14 CFR §121 and §135, the analyses supported the hypothesis that a "U"-shapedrelationship exists between the age of professional pilots holding ATP or commercial andfirst- or second-class medical certificates and their accident rate. Second, the accident ratefor the 60-63 age group was statistically greater than the accident rate for 55 or 56 to 59year old pilots in the a priori planned comparisons. Third, the main effect for age wasstatistically significant in all analyses. These findings suggested that the probability of anaviation accident under §121 and §135, as a function of pilot annual flight hours, wasrelated to pilot age."