Aircraft and cycles on them
How many cycles an aircraft accumulates depends on how an airline operates it, but most aircraft have a design limit for total hours and total cycles. These limits are very different depending on the service environment the airplane was designed for. Enforcement regarding restrictions when aircraft approach these limits is more up the the FAA or a country's regulatory agency than it is up to the airlines. Some airlines however are fussier about that than others. Some airlines will purchase an aircraft which is approaching its limits, or approaching a major check, just because they're cheaper, and may simply scrap the plane when it passes the threshold, or evaluate its worth at that time in regard to paying for a major overhaul or check. Orient Thai Airlines does this in fact with many or most of its purchases.
There have also been many limit extension programs for aircraft, and some have gone beyond factory spec when inspections determined the structure was still sound when at these limits.
DC-9s and 737s, for example, are meant for high cycle service environments, where flights are often 1-hour or much less. As these aircraft age is not uncommon at all for them to have more cycles on them than flight hours. The Aloha Airlines 737-200 which back in 1988 had 89,000 cycles was an extreme example, but it had something like only 30,000 hours (I am quoting that from memory).
727s often have had between 60k and 80k hours, and 40k cycles, where these aircraft flew longer stage lengths, on average.
747s, DC-10-30s, etc have frequently approached 100k hours, but had 20k cycles or less, due to their very long flight sectors. Northwest had a DC-10-30 with over 130,000 hours at retirement, and it was still airworthy. (People who say the DC-10 is not a sturdy or quality built aircraft are incorrect). A tiny little new airline, Air Baltia or something like that, wants to start flying with a former NW 747-200 which has over 105,000 hours as well. These aircraft are not built for the rigorous cycle accumulations like the 737 and DC-9 were, although there were domestic models of both the 747 and the DC-10.
Some airlines are much better, or more purposely, use-up an aircraft's cycles or hourly limits than others. In the mid 1990s, when a large number of original 727-200s were retired by United, Continental, and Northwest, most all these planes had been built in the 1968-1970 time frame. United's planes all had around 65k hours, whereas Continental's had approached 80k often. This is because throughout the life of the planes at CO, that airline utilized their planes, more, every day, than United did, as a management decision. Today, a similar scene would be encountered when comparing a somewhat recently retired legacy United 737-300 vs. a Southwest Airlines 737-300, especially in cycles accumulation.
So, in a nutshell, hours and cycles depend on the type of plane, and the owner/operators it had in its lifetime.
