Ops look at the route options for the day. There is a big saving in ATC route charges by going via T9 or T16. If the extra flight time (read fuel cost) is not excessive then it is worth going on the longer route. I recall someone quoting a figure of about $1000 dollar saving per sector on the overflight charges if using T16. You avoid France, Spain, Portugal and Casablanca if using T16.