I really love the game! But the duration calculations are unclear. If I give a 150 km letter to the starting raven with a speed of 95 km/h, I would expect the time to delivery to be a little over 1.5 hours. Instead, it's 3.1 hours and I haven't the faintest idea why.
This makes it a little hard to make sure I'm picking the right birds for the job which is rather distressing -- Queen Isadora has demanded the best of avian logistics after all!