http://travel.yahoo.com/p-interests-212676...2xrA29uLXRpbWU-

I think the way they measure can be a bit unfair on the larger airlines, the further and more destinations you fly the more likely you are to be late, if a plane is coming in from say Australia to London, it's more likely to be late arriving and consequently more likely to be late leaving again, whereas the smaller regional airlines are flying much shorter distances and are more likely to be on time, with the knock-on effect of being on time departing again.