Recently there have been reports that aircraft have occasionally dumped kerosene before landing. There is no such dumping of fuel in regular flight operations.
Fuel dumping is subject to a mandatory internationally recognised standard procedure to be used exclusively for air traffic safety. This procedure is only used in rare emergency situations. According to the German Aviation Association (BDL), this happened on average only 21 times a year between 2010 and 2017, so it is extremely rare.
The need for this measure may arise from the fact that the take-off weight of large passenger aircraft may exceed the maximum permissible landing weight, depending on the amount of fuel used. If this difference between the maximum take-off weight and the maximum permissible landing weight is particularly large, the aircraft must be able to dump fuel for safety reasons. Therefore, only long range aircraft such as the A350 or A380 have a fuel dump mechanism. For smaller aircraft, such as those in the A320 family, this is not necessary because they are lighter. When designing these systems, the aircraft manufacturers strictly abide by the requirements from certification authorities such as EASA in Europe.
Dumping means that an aircraft can land safely during a medical emergency, for example, where every second counts. Other factors also play a role in the decision to land, such as aircraft design, runway length and current weather conditions. As a general rule, no aircraft operator gains from dumping valuable fuel for no reason and without there being an emergency. Such a measure would not be cost effective either.
The implementation of such an emergency measure is done in consultation with the air traffic control unit in charge, such as German Air Traffic Control (DFS), and only at a minimum flight altitude in an airspace with low air traffic density over uninhabited areas. In addition, the amount of kerosene dumped is strictly limited.
Further information can be found on the German website of the BDL: https://www.bdl.aero/de/veroffentlichungen/luftfahrt-aktuell/luftfahrt-aktuell-15/#
Status: Sept 2018