What Were The Busiest Routes In 2021?

Domestic flights dominated the list of busiest routes in the world during 2021, led by a leisure service in South Korea.

Credit: Jung Yeon-je/AFP/Getty Images

In a year characterized by border restrictions and divergent entry requirements, it is unsurprising that the list of busiest routes in 2021 is dominated by domestic services in some of the world’s largest aviation markets.

Analysis of OAG Schedules Analyser data shows that 49 of the top 50 routes by flight frequencies were domestic, with the sole international route being a 15-min. flight between the Caribbean islands of St Barthelemy (SBH) and St Maarten (SXM).

Eleven of the 50 busiest were between destinations in China, while India, Indonesia, Japan, South Korea and the US each had four domestic routes apiece.

However, despite another year of uncertainty for the aviation industry, one certainty when compiling a list of busiest routes seems to be that the table will be topped by a 450-km domestic service between Seoul Gimpo (GMP) and Jeju (CJU).

OAG data shows that there were some 85,880 flights between GMP and CJU in 2021—equivalent to about 235 per day. The route transports mainly leisure passengers from South Korea’s dense capital city to the island of Jeju, famed for its white sandy beach resorts and volcanic landscape.

Nine carriers competed in the GMP-CJU market in 2021, led by Korean Air which offered about 4 million two-way seats. A further 3.9 million were available onboard Asiana Airlines, while Jeju Airlines provided 2.9 million seats.

In total, capacity between the destinations was almost 17.1 million seats—down by just 1.9% on the figure offered in 2019.

The second busiest route in 2021 also connected two points in South Korea, linking Seoul Gimpo and Busan (PUS). There were about 34,900 flights between the airports, representing an increase of 65% compared with pre-pandemic levels two years ago.

Jeddah (JED)-Riyadh King Khalid (RUH) ranked as the third busiest with 32,405 flights; Fukuoka (FUK)-Tokyo Haneda (HND) was fourth with 32,400 flights; and Sapporo New Chitose (CTS)-Tokyo Haneda was fifth with 31,495 flights.

While the 31-km service between St Barthelemy and St Maarten topped the list of international routes, only seven other overseas services made the top 400 busiest routes worldwide. The second busiest was between Orlando (MCO) and San Juan (SJU) in Puerto Rico, followed by Bonaire (BON)-Curacao (CUR), Houston (IAH)-Mexico City (MEX) and Cairo (CAI)-Jeddah.

Of the top five overall busiest routes in 2019, just GMP-CJU and FUK-HND make the top five this time around. Melbourne (MEL)-Sydney (SYD) dropped from second to 32nd in the rankings, while Hanoi (HAN)-Ho Chi Minh City (SGN) fell from third to 45th. Mumbai (BOM)-Delhi (DEL) also plummeted from fifth to 40th.

Looking at international services, the busiest route in 2019 connected Kuala Lumpur (KUL) and Singapore (SIN) with almost 31,000 flights. However, the route ranks as only the 1,407th busiest overall in 2021, totaling just 3,800 flights during the year.

Frequencies between Hong Kong (HKG) and Taipei (TPE), ranked as the second busiest international in 2019, were down by 84% in 2021, and by 86% between Jakarta (CGK) and Singapore, ranked as the third busiest two years ago.