Scheduled maintenance frequencies and time limits for commercial transport aircraft are generally quantitative. Their numerical values are seldom, if ever, derived by calculation, however. At best, they are quantified expressions of good subjective judgement.This paper submits the premise that if a scheduled maintenance frequency or time limit is worth quantifying, it should also be possible to rationally calculate the approximate numerical value of that frequency or limit. The significance and availability of measurable variables required to implement such a calculation are examined. A tradeoff equation is developed and submitted as a feasible response to the need for a more rational and less emotional approach to the establishment of scheduled maintenance frequencies.