Why don't flights travel in a straight line?

Answer 1

There are a number of factors in deciding flight paths. There are incoming planes and outgoing planes from an airport and each must have a different flight path. There are also civil restrictions on flying over populated areas, which means at certain times of the day some flight paths are off limits. Often a coastal city must be approached from the sea, so the flight path may involve approaching the city by a rural flight path to miss populated areas and then several tight turns to approach the airport from the ocean.