From an accountant's viewpoint, the provision of reserve fuel costs money (the fuel needed to carry the hopefully unused reserve fuel). Techniques known variously as reclear or redispatch or decision point procedure have been developed, which can greatly reduce the amount of reserve fuel needed while still maintaining all required safety standards. These techniques are based on having some specified intermediate airport to which the flight can divert if necessary;^[1] in practice such diversions are rare. The use of such techniques can save several tons of fuel on long flights, or it can increase the payload carried by a similar amount.^[3]

A reclear flight plan has two destinations. The final destination airport is where the flight is really going to, while the initial destination airport is where the flight will divert to if more fuel is used than expected during the early part of the flight. The waypoint at which the decision is made as to which destination to go to is called the reclear fix or decision point. On reaching this waypoint, the flight crew make a comparison between actual and predicted fuel burn and check how much reserve fuel is available. If there is sufficient reserve fuel then the flight can continue to the final destination airport, otherwise the aircraft must divert to the initial destination airport.

The initial destination is positioned so that less reserve fuel is needed for a flight from the origin to the initial destination than for a flight from the origin to the final destination. Under normal circumstances little if any of the reserve fuel is actually used, so when the aircraft reaches the reclear fix it still has (almost) all the original reserve fuel on board, which is enough to cover the flight from the reclear fix to the final destination.

The idea of reclear flights was first published in 'Boeing Airliner' (1977) by Boeing engineers David Arthur and Gary Rose.^[3] The original paper contains a lot of magic numbers relating to the optimum position of the reclear fix, etc. These numbers apply only to the specific type of aircraft considered, for a specific reserve percentage, and take no account of the effect of weather. The fuel savings due to reclear depend on three factors:

• The maximum achievable saving depends on the position of the reclear fix. This position can't be determined theoretically since there are no exact equations for trip fuel and reserve fuel. Even if it could be determined exactly, there may not be a waypoint at the right place anyway.
• One factor identified by Arthur and Rose which helps achieve the maximum possible saving is to have an initial destination which is positioned so that descent to the initial destination starts immediately after the reclear fix. This is beneficial because it minimises the reserve fuel needed between reclear fix and initial destination, and hence maximises the amount of reserve fuel available at the reclear fix.
• The other factor which is also helpful depends on the positioning of the initial alternate airport.

Alıntı adresi : http://en.wikipedia.org/wiki/Flight_planning
Özet olarak bir karar noktası belirlenip bu noktaya gelindiğinde yeterli yakıt var ise varış noktasına devam ediliyor. Yeterli yakıt yok ise yedek meydana divert ediliyor. Fakat aklıma bir soru takıldı. Eğer burada bahsettiği initial destination dediği nokta bizim bildiğimiz yedek meydan ise yedek meydanın her zaman varış noktasından daha önce olması gerekiyor. Sonuçta kalkışı yaptık ve yakıtımız yetmediği için bir karar noktasında divert etmeye karar verdik bu durumda divert edilecek meydanın varış meydanından daha yakın olması gerekir.