As the crow flies
This means in a straight, direct line without making any of the detours involved in following a road that may twist and turn. The allusion is obviously the ability of crows to fly in a straight line from A to B, however, the choice of the crow remains puzzling. Crows do not fly for long distances in straight lines, at least, no more so than many other birds. They tend rather to fly in large, wheeling arcs as they search for food. The expression has been in use since the 18th century and in Scotland, the expression crow roads is still used to describe straight, direct roads.