EX Bus Driver, I suspect it has something to do with using some aircraft as freighters.
For example, look at the differences for the B727-200 and B727-F. The DOC is substantially higher for the freighter (because freighters burn more full per mile given their payloads). I think the data is an industry average for each type, and you'll notice that the DOC seems noticeably higher for those types where a fairly large percentage of the total airframes (in service) are used for freight, including the A300-600.
I know the chart says (for passenger models only) but I don't really think that's true for all types in the chart. Just for fun, look at the difference in the DOC for the A300-600 and the B777, WOW!
[ 08 December 2001: Message edited by: Flight Safety ]