Airlines put 1,048,829 seats on the Jeju–Seoul Gimpo route in November 2026, making the South Korean island shuttle the world's busiest domestic air corridor for another month — even after carriers cut its capacity by 24% year on year. OAG, the aviation data firm, ranked the 10 heaviest domestic routes by scheduled seats, and six of them lost capacity versus November 2025. The list runs from Jeju–Seoul down to Jeddah–Riyadh, which sits in 10th despite a 28% cut.

That's the core of this story. These rankings don't measure how many people want to fly. They measure how many seats airlines choose to sell, and those decisions now respond to fuel bills, full airports and security threats rather than passenger appetite.

What drives the numbers?

Geography built this list. Nine of the world's 10 heaviest domestic routes sat in Asia-Pacific in 2024, according to CNBC, because islands, elongated countries and distant megacities leave few practical alternatives to flying. A short hop is simply the normal way to travel.

Pressure this year comes from outside aviation. Qantas figures reported by ABC News put jet fuel refining margins at a peak of around $US120 per barrel during the Iran war. Thousands of miles away, Reuters reported that King Khalid International Airport in Riyadh halted operations on Oct. 10 after an attack that killed 13 people, reopening only partially on Oct. 25. One regional conflict is reshaping schedules on corridors that share nothing else.

How does each route stack up?

• Jeju–Seoul Gimpo: 1,048,829 seats, down 24%. Asiana cut Jeju domestic seats 26% for the summer season, per Financial News, while Jeju Air grew 10%. The drop is a carrier-by-carrier decision, not an industry retreat.
• Sapporo–Tokyo Haneda: 988,247 seats, flat. The only growth-free fixture in the top three. Airlines kept last year's schedule essentially intact, and that was enough.
• Fukuoka–Tokyo Haneda: 964,157 seats, down 2%. Third again, as it was in 2024 per CNBC. "Haneda airport is effectively full so that new capacity has had to go to Narita," OAG chief analyst John Grant told CNBC in 2024. Meanwhile, Fukuoka–Incheon international seats grew 10%.
• Hanoi–Ho Chi Minh City: 909,145 seats, down 7%. Still fourth, because fifth place is far behind.
• Melbourne–Sydney: about 690,000 seats, down 7%. Qantas, which ABC News reports estimates its fuel bill at $3.1–3.3 billion for a single half-year, has cut domestic capacity across Qantas and Jetstar, moved some aircraft to Paris and Rome, and raised fares. The airline said it "retains optionality to take further actions to mitigate fuel cost increases over time."
• Shanghai Hongqiao–Shenzhen: about 687,000 seats, up 5%. The fastest grower on the list, just 2,778 seats behind Melbourne–Sydney. Business Traveller reported the route was down 4% in August 2026, so the November gain is real but unproven as a trend.
• Tokyo Haneda–Okinawa Naha: 685,658 seats, up 3%. A holiday route flown like a commuter shuttle. JTA is resuming Osaka Itami–Naha service for the first time since 2007, and also flies Naha–Taipei, per the JAL Group.
• Mumbai–Delhi: 684,478 seats, up 3%. Growth against the grain — OAG says Indian carriers cut domestic capacity 3.3% overall.
• Beijing–Shanghai Hongqiao: 631,426 seats, down 1%. Air China and China Eastern operated about 90% of daily flights as of May 2025, per Shanghai Airport. Their May–August 2025 ticket-transfer trial signals a route both defend.
• Jeddah–Riyadh: about 617,000 seats, down 28%. Riyadh's airport reopened partially on Oct. 25 with domestic flights in Terminal 1; Flightradar24 showed little activity that first day. Houthi military spokesperson Yahya Saree said the airport would "never be safe," per Reuters. Some scheduled seats may never be flown.

Which rankings could flip?

Margins are thin near the middle. Melbourne–Sydney leads Shanghai–Shenzhen by fewer than 3,000 seats. Haneda–Naha beats Mumbai–Delhi by roughly 1,200. Beijing–Hongqiao leads Jeddah–Riyadh by about 14,000. One schedule change on either side of any of those pairs reorders the list.

Each position, in other words, is a test a route passes this month — not a title it holds for good.