New interim final rules on a controversial aging-aircraft-inspection program for multi-engine airliners operating under Parts 121, 129 and 135 took effect last month. The rules require such airplanes to undergo inspections and records reviews after their 14th year of service and at seven-year intervals thereafter. The mandate essentially disregards objections raised by the Regional Airline Association and a number of U.S. regional airlines over the cost implications of the new rules’ damage-tolerance requirements.