Aircraft are specifically designed to operate routes of a certain duration, so the plane that you will be flying on will typically be a plane designed to fly that type of route. Most aircraft life times are measured in cycles and the aircraft lifespan is established by the manufacturer, usually based on take-off and landing cycles. The fuselage is most susceptible to fatigue, but the wings are too, especially on short hauls where an aircraft goes through pressurization cycles every day. Aircraft used on longer flights experience fewer pressurization cycles, and can generally last longer. Aircrafts designed for long-haul flights typically are designed for flight cycles involving long cruises, between take-off/landing. Meaning that, for instance, the lifetime for such aircraft may be established as 50 000 flight hours but only 8000 cycles, whichever comes first => It is not economically beneficial to use long haul aircrafts on flights which are shorter than 6 h.