Originally Posted by
3Cforme
Care to show your work on that one? UK Air Passenger Duty alone (and then there are airport fees) exceeds U.S. taxes. You may have a BA thing going on.
Their point was that USA-LON-USA on BA is more expensive than LON-USA-LON on BA, as BA imposes a higher YQ on ex-US itineraries. APD for both would be the same, charged once.