Close maintenance, improve designs and check material
For aircraft manufacturers, the fact that airlines rely on safe aircraft types means that designs are constantly improved and aircraft are closely maintained. Even the smallest incidents, such as the breakage of a component, are meticulously investigated and entire fleets are called in for inspection. The aircraft industry, essentially Boeing vs. Airbus, relies on two basic ideas, one is meticulous maintenance, the other is redundancy, i.e. all important parts are at least duplicated, in important places even triplicated. This approach ensures that if one part fails, the function of the system remains unaffected. The components themselves - right down to the smallest screw - are specified and approved for their area of application. They are also subject to a fixed period of use, after which they are replaced during maintenance, regardless of their condition. This is worthwhile, since aircraft are used safely for many years. All airlines, including low-cost carriers, are subject to maintenance intervals.