 The airport's runway was too short to allow large aircraft such as the Boeing 747 to operate intercontinental routes out of Durban, and the resulting decrease in international air traffic caused Durban to become marginalised with respect to Johannesburg and Cape Town.Upgrading Durban International Airport was considered but a study published in 2007 found that the existing airport would still have serious constraints and would reach its maximum potential by 2025, after which there would be no choice but to develop KSIA.It was also found that it would be 95% more expensive to operate Durban International Airport to its full potential and only then develop KSIA, than it would be to develop KSIA immediately.