From an eagle's eye view, a mile up, seems like a curve to me.
You often hear the term the "eye of an eagle" ... this proves it's true!

 
An eagle’s flight from the top of the world’s tallest building to his handler below.  The eagle was fitted with a camera then released from the top of the 2, 715 foot Burj Khalifa tower in Dubai.  The eagle has no idea where the tiny speck of land was that his handler is standing on or what it looked like among all of the other lands and buildings and people.  Somehow from that altitude, the eagle actually picks out and recognizes the trainer from all of the other objects, people, etc.  You can see him looking, looking, looking for the trainer, completely invisible to a human eye and the camera, then folds his/her wings and drops like a bullet straight to the trainer..very cool.  What surprised the experts is not only how efficiently the eagle spots his trainer from that altitude, but how smooth its flight is with no camera shake whatsoever, even when it goes into a power dive.    Enjoy
 
https://www.youtube.com/embed/6g95E4VSfj0?rel=0