Seoul's Incheon airport and the Delhi airport bagged the top two positions among the 22 airports handling 25 million to 40 million passengers. The ACI survey is one of the most credible assessments of airports' service standards.Close to 1,500 passengers from each of the 180 airports surveyed were asked to rate service standards between the arrival terminal and the departure gates of an airport. ACI then divided airports into five categories depending on the passenger load they handled, ranging from 2 million passengers to more than 40 million passengers.
Last year, Mumbai airport ranked second in the 15 million to 25 million passengers category. Although it slipped to the third place this year, the airport improved it's performance rating from 4.39 to 4.61 on a scale of five. Delhi did better at 4.72.