What is the lifespan of commercial airframes (in general)?
Metal fatigue is normally the limiting factor of an aircraft's lifespan. Fatigue cracks build up every flight (at start &amp; landing), called a cycle. Therefore the design life of an aircraft is typically given in cycles.


Metal fatigue cracks, source: Boeing



For long haul aircraft, that make relatively few cycles, the design lifespan is in the order of 40 000 cycles. For short haul the number is higher, sometimes up to 111 000 cycles.

For example, the Boeing 747 has a design number of cycles of 35 000, the MD-80 has 110 000.

An aircraft should be operable for about 30 years before reaching the cycle limit. The lifetime can be stretched by special inspection and maintenance programs.