ENG: how do airlines ensure jet safety?
To assure passenger safety, airlines across the globe are required to complete a constant and effective inspection and maintenance program for its fleets.
Before the mid-1950s, when high-speed commercial air travel began, aircraft maintenance tasks were being developed by flight crew and mechanics. At the time, the aircraft's needs for maintenance were based on individual experience rather than a deep analysis of the plane.
However, the introduction of large commercial jetliners, such as narrow-bodies Boeing 707 and Douglas DC-8 in 1954, caused a necessary change to this procedure and manufacturers became aware of the importance of aircraft maintenance regulations, particularly when it came to ensuring passenger safety.
Depending on aircraft type, a specific amount of flight hours (FH), or flight cycles completed, airlines initially used to divide maintenance processes into separate parts. These are more commonly known as A, B, C, and D checks.