Revealed: The World’s Busiest Routes In 2021

The world’s top-20 routes in 2021 have been revealed, with Jeju to Seoul Gimpo taking the leading spot by flights tracked. All 20 routes were domestic, and most were in Asia. Data doesn’t indicate how many passengers were carried, how full each flight was, or what each passenger paid, but it shows the busiest routes by flights operated.

Jeju to Gimpo
With an average of almost 100 daily departures, the short link from Jeju to Seoul Gimpo was the world’s number-one route last year. Photo: Getty Images

The world’s top-20 routes in 2021

The 280-mile (450km) service from Jeju – often known as the ‘Hawaii of South Korea’ – to Seoul Gimpo had 71,388 flights tracked last year, making it overwhelmingly the world’s leading airport pair. The information is from a comprehensive report by Cirium that looked at the overall performance last year and what may happen in the current year.

All of the 20 routes were domestic, as is the case every year. Of course, the international market was severely affected by so many border international restrictions. Indeed, Cirium shows that passengers carried between January and September 2021 accounted for 79% of the world’s total traffic, up from 58% in full-year 2019.

Thirteen of the top-20 were within Asia proper, especially domestic China, while three involved Latin America and two the US. While not surprising, no Europe route featured, although it may be slightly different if city-pair was examined instead. The lack of domestic Australian flights is conspicuous, obviously from a significant and prolonged lockdown and inter-state border closures.

The world's top-20 routes in 2021
Usually, Sydney-Melbourne would be the world’s #2 route by this measure, while Sydney-Brisbane would also be in the top-20. Image: Cirium’s 2021 Airline Insights Report.

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Jeju to Seoul Gimpo

The South Korean island of Jeju is so popular because it is easy and cheap to reach, involves a short flight (often less than 50 minutes to/from Gimpo), and has some of the best scenery and beaches in South Korea.

The huge amount of air service is because there is no real alternative to reach the island. Nine airlines operated last year, as shown below. Almost half of the flights were by Asiana and Korean Air, rising to a substantial majority when their subsidiaries are included.

  • Asiana
  • Korean Air
  • Jeju Air
  • Jin Air
  • T’way Air
  • Air Busan
  • Air Seoul
  • Air Premia
  • Hi Air
Jeju to Gimpo
When writing, it is nearly 21:00 in South Korea. Nonetheless, there are still multiple flights between Jeju and Gimpo and back. Highlighted is Asiana flight OZ8976, operated by HL7772, a 159-seat A320 delivered in May 2008. The carrier has just two A320s. Image:

The USA’s leading route

The world’s 14th busiest route – and number-one in the US – was Los Angeles to San Francisco, some 337 miles (543km) apart. It was followed by Las Vegas to Los Angeles, which replaced New York LaGuardia to Chicago O’Hare.

Los Angeles-San Francisco usually is the USA’s number-one airport-pair, and the pandemic didn’t alter its ranking. This is despite California being particularly severely affected by coronavirus (especially earlier on) and San Francisco having the USA’s most significant capacity drop last summer.

JetBlue Airbus A321-231 N971JT (2)
JetBlue added Los Angeles to San Francisco in October 2020. No wonder it had the lowest seat load factor of all operators (see below the photo). Photo: Vincenzo Pace | Simple Flying.

484k passengers in the latest available quarter

According to the Department of Transportation’s T-100 dataset, Los Angeles to San Francisco saw 484,051 passengers in the third quarter of 2021 (July-September), the latest period available to the author. That was up by 38% over the prior quarter but down by nearly half versus Q3 2019, reflecting the continued lack of business travel.

With 131,192 passengers, United was the dominant carrier. It filled 85.1% of its seats, helped by its system fare being 16% lower than in Q3 2019. Almost six in ten passengers were local (i.e., they flew only between the two airports), a meaningfully higher proportion than usual.

United carried more passengers than any other airline, followed by Alaska (98,066, 86.2%), Delta (72,080, 84.4%), JetBlue (71,879, 65.3%), Southwest (65,894, 79.9%), and American (44,940, 86.5%).

Have you flown any of the top-20? Share your experiences in the comments.