Influence of fog on aircraft delays at Jomo Kenyatta international airport, Nairobi, Kenya

Abstract

In this study, the influence of fog on aircraft delays at JKIA for the period 2000 to 2005 is considered. Delays are defined in terms of the difference between the actual flight time and that projected by the air traffic control system. Meteorological and aircraft delays data have been analyzed using statistical techniques to achieve the objective. Results indicate that fog occurs at Jomo Kenyatta International Airport (JKIA) is between 2100 to 0700 UTC and is rare between 0800 and 2000 UTC. Fog occurrence per month is highest in April, November and December, which also coincides with seasonal rainfall periods. Results also reveal that low dew point depressions (difference between dry bulb and dew point temperatures) are favourable for fog formation. Since the highest frequencies of daily fog occurrences have been found to coincide with the peak hours of aircraft arrival, it may be appropriate for flight planners to use this information and probably consider rescheduling of flights in the months of high fog occurrence to periods outside these peak hours. The cost of aircraft delay due to fog has been estimated from the number of delays in minutes at a cost of US$ 100 per minute. This has resulted to an estimated total loss in excess of KShs 50,000,000 during the period 2000-05 arising from delays alone. If the costs of diversions, which are exponential, were taken into consideration, the losses would be in excess of KShs 1,000,000,000. Although the results indicate significant fog impact on flight delays at JKIA, total quantification on the impacts of fog on aircraft delays is difficult because fog is only one of the many factors influencing aircraft landing or take-off at JKIA. Other factors need to be studied and be understood. This study is mainly diagnostic in nature.