According to an annual report by UK-based firm OAG, Singapore - Kuala Lumpur is the world's busiest international route. It must be mentioned that the duration of the flights between the two destinations is barely more than an hour. The report was made by determining the frequency of flights both ways.
From March 2017 to end of February 2018, 30,537 flights covered the Singapore - KL route that topped the list, with an average of 84 flights every day. The route is covered by a host of budget airlines including AirAsia, Jetstar, Scoot, Malindo Air as well as Singapore Airlines and Malaysian Airlines. Around 4 million people were transported in those flights, the report mentioned.
However, if the number of passengers is to be counted, then the busiest route would be Hong Kong - Taipei with 6.5 million passengers, with Singapore - Jakarta at 4.7 million following closely. The Singapore - KL route would be third on the list.
OAG also mentioned that 14 of the 20 busiest international routes are in Asia. Outside of Asia, New York's LeGuardia and Toronto Pearson with 16,956 flights topped the list.
Singapore - KL is followed by Hong Kong-Taipei with 28,887 flights and Jakarta - Singapore with 27,304 flights, Hong Kong - Shanghai with 21,888 flights, Jakarta - KL with 19,849 flights, Seoul - Osaka with 17,488 flights, Hong Kong - Seoul with 17,075 flights, New York - Toronto with 16,956 flights, Dubai - Kuwait with 15,332 flights and Hong Kong - Singapore with 15,029 flights.
However, the busiest domestic air routes are a far cry from even the busiest international routes. The world's busiest domestic air route is between Seoul and Jeju, a popular holiday island in South Korea. In 2017 alone, 65,000 flights covered the route, with almost 180 per day.