According to aol.com, they call August 23 "Cheap Flight Day" because it's the day most airfares drop on many routes.

If you haven't had a summer vacation yet, wait to take off Aug. 23 and beyond and chances are very good you'll save some money.

Aug. 23 marks the start of the fall travel season because kids are back in school and leisure travel drops significantly.  It's also when airfares drop anywhere from about 10 to 20 percent and sometimes more, depending on departure and destination cities.

To get the best fare, check out recent sales from airlines and look at the travel periods covered by the deals.  The August 23 price drop is good for both U.S. domestic fares and flights to Europe.