Times not to fly:
Best time to fly:
Airlines companies have to get their planes to certain locations by certain days of the week. They try to pack as many flights full as possible, but many flights simply occur because they need to get the plane to another location.
Friday/Sunday evenings & Monday mornings are peak travels times for most people because of 9-5, Monday-Friday jobs. So the airlines companies schedule more flights around these times, and thus the planes are already at the location they need to be in during these times.
Saturdays are essentially make-up days to get planes back to their peak volume locations for the following sunday/monday boom.
Almost every single flight I have booked on a Saturday I have gotten bumped up to first class. Even with the lowest status possible on a particular airline.