I'm not a pro within these terms, but what came to my mind:
- Only the aircraft costs themselves pay off the faster, the more hours the a/c is in the air (given some revenue on these flights). But fuel and crew costs, maintenance, landing fees are per-flight-values.
- Carriers which tend to keep their a/c for long time, may prefer to keep some life in them.
- The shorter the routes, the lower the utilization rate. But not all airlines are able to fly longer routes -- and I'll bet there are very lucrative short flights.
's commuter a/c, an utilization of 8 hours may not be THAT low, given that U.K. is not the size of the States...
Just my few cents... (too much work to be done here at home...