I've wondered for a while why the Avios I'm awarded always seems to be a little bit less than the minimum actual distance flown between two airports. Last week when we boarded at ATH, the screen display showed a distance of 1,509 miles to LHR. This corresponds pretty well with a "great circle" distance calculator on my computer which gives 1,511 miles. In fact BA award me 1,494 miles (exclusive of any bonus) for the journey. Although I don't have the figures to hand, I had a similar experience on the route to HEL recently too.

As the "great circle" distance is the minimum possible one between any two points, my question is whether BA have found some secret way of taking a slice through the earth's surface to calculate a shorter distance???