Still, there is reason to expect that fatigue may affect airplanes increasingly in the future. For one thing, there is little difference in performance and utility between airplanes built just after World War II and those built 10 years ago, and so used airplanes, even quite old ones, retain their value well. The high and rising price of new aircraft makes old workhorses, like the Cessna 402, attractive to small operators. The average age of the entire civil fleet, excluding airliners, therefore tends to increase. In the quest for productivity, utilization rates rise. At the same time, ex-military aircraft, such as C-130s, find their way into various civil applications, like firefighting, where they are subject to high stress levels but may no longer receive the systematic maintenance that they got during their military careers. Finally, more large aircraft are being designed in accordance with "damage tolerance principles" under which some fatigue cracking is expected, but is supposed to be detected and corrected under a program of regular inspections.