The growth of Hong Kong also put a strain on the airport's capacity. Its usage was close to, and for some time exceeded, the designed capacity. The airport was designed to handle 24 million passengers per year, but in 1996, Kai Tak handled 29.5 million passengers, plus 1.56 million tonnes of freight, making it the third busiest airport in the world in terms of international passenger traffic, and busiest in terms of international cargo throughput. Moreover, clearance requirements for aircraft takeoffs and landings made it necessary to limit the height of buildings that could be built in Kowloon. While Kai Tak was initially located far away from residential areas, the expansion of both residential areas and the airport resulted in Kai Tak being close to residential areas. This caused serious noise and engine pollution for nearby residents and put height restrictions, which were removed after Kai Tak closed. A night curfew from 11:30 pm to 6:30 am in the early morning also hindered operations.