Well I don't know... I'm just heading to the airport to pick up my re-issued DONE4 that's now a DONE5 and I can assure you they added the extra continent charge, as well as the applicable new taxes. Now how they came up with the net number for taxes (flights added, flights deducted etc.) - well, that's where the Dark Arts come in to the picture. I'm convinced that each airline's revenue management department has a Slytherin Desk where someone looks at the PNRs, hauls out a wand and shouts, "Crucio!"