With most airlines, free flights generally start at 5,000 to 7,500 miles per one-way segment. So to book a round-trip flight, you typically need at least 10,000 to 15,000 miles.

The number of points required for a "free" flight varies wildly depending on the airline, the distance, and the time of travel, as most carriers have moved to "dynamic pricing." On average, for a standard domestic one-way flight in the United States, you typically need between 7,500 and 15,000 points. For example, Southwest Airlines allows redemptions for as little as 5,000 points for short "wanna get away" hops, while legacy carriers like Delta or United might charge 12,500 points for a similar route. International flights require a much larger balance; a round-trip ticket from the US to Europe usually starts at 60,000 to 80,000 points in economy, though "saver" awards can sometimes be found for less. If you are looking for Business or First Class, be prepared to spend anywhere from 150,000 to 300,000 points. It is also important to remember that a "free" flight isn't entirely free; you are still responsible for paying government taxes and airport fees, which can range from $5.60 for a US domestic flight to over $800 for a flight out of London Heathrow due to their high "Air Passenger Duty." To maximize value, many travelers aim for a redemption rate of at least 1.5 to 2 cents per point relative to the cash price of the ticket.