The A check is performed approximately every 400-600 flight hours, or every 200–300 flights, depending on aircraft type. Aircraft operators may perform some work at their own facilities, but often checks, and especially the heavier checks, take place at maintenance, repair and overhaul (MRO) company sites. A and B checks are lighter checks, while C and D are considered heavier checks. This allows for more flexibility in the scheduling of maintenance to minimize aircraft downtime.Īirlines and airworthiness authorities casually refer to the detailed inspections as "checks", commonly one of the following: A check, B check, C check, or D check. Modern aircraft with MSG-3-derived maintenance programs employ usage parameters -such as flight hours, calendar time, or flight cycles-for each required maintenance task included in the MRBR. The MRBR is an approved set of aircraft initial maintenance requirements as prescribed by the Appendix H to para. In the United States the FAA directs that initial aircraft maintenance requirements be generated for each aircraft type in a Maintenance Review Board Report (MRBR) based on the analysis performed as outlined in ATA "MSG-3 Operator/Manufacturer Scheduled Maintenance Development" document (MSG-3 is for Maintenance Steering Group – 3rd Task Force). The CAMP includes both routine and detailed inspections. Each operator prepares a Continuous Airworthiness Maintenance Program (CAMP) under its Operations Specifications or "OpSpecs".
Airlines and other commercial operators of large, or turbine-powered, aircraft follow a continuous inspection program approved by the Federal Aviation Administration (FAA) in the United States, or by other airworthiness authorities such as the Transport Canada Civil Aviation Directorate (TCCA), or the European Aviation Safety Agency (EASA).