Originally Posted by
railways
The tier bonus appliies to actual distance flown, so in your first example it is 3,081 x 0.75 = 2,311. So you get (3,081 x 0.5) + 2,311 = 3,852 miles.
Ahh, that does of course make sense.
I feel kind of stupid for ignoring that explanation.
Thank you so much, "mystery" solved