Statistical Appraisal of Maximum Age Requirement for Commercial Airplanes in Nigeria

Abstract

This paper proposes and uses a factor of relative age difference for each plane termed relative “plane age”, index. Using these indexes and their ranks, it is shown that the enunciated mandatory upper age limit of 20 years is approximately the mean age of the commercial planes in the country estimated to be 20.7 years, but higher than the median age of the planes found to be 19.4years. Thus if median age of 19.4 or about 19 years rather than 20 years is to be set as the required upper age limit, then only about 33 or 34 rather than 37 commercial planes would be properly eligible to fly Nigeria’s airspace. Statistically significant differences in age are found to exist between commercial planes that may importantly affect their operation. Relative “plane age” indexes that are positive with a value of 17 or larger so that the corresponding planes are younger than at least 42 and older than at most 25 other planes and aged at most 15.3 years are statistically significant; while those relative “plane age” indexes that are negative with a value of at most 20 so that the corresponding planes are younger than at most 23 and older than at least 43 other planes and aged at least 21.2 years are statistically significant. Hence if age is to be considered as a statistical factor affecting air-worthiness of commercial planes, then the upper age limit of 15.3 or 15 years should be preferred and used as a selection eligibility criterion for commercial planes in Nigeria. This will in effect imply that no plane aged above 15.3 years may be allowed to fly resulting in only about 26 commercial planes rather than 37 as is the case under the current dispensation being able to properly and normally use Nigeria’s airspace.