South Korea's Incheon has become the world's busiest airport by international passenger traffic for the first time, new figures show.

Incheon International Airport, the main gateway to South Korea, served 38.4 million international passengers for the first six months of this year, according to preliminary data from the Airports Council International.

London Heathrow Airport ranked second with 37.79 million passengers, followed by Singapore's Changi Airport with 34.53 million.

Incheon's airport attributed its rise partly to the diversion of passengers from aviation hubs in the Middle East because of the conflict between the US and Iran.

Dubai International Airport, which ranked second both in 2024 and 2025 based on full-year statistics, is expected to fall outside the top five this time.

London's Heathrow airport ranked fifth in 2024 and seventh in 2025, while Incheon ranked 12th and 13th, respectively.

Some passengers who previously transited through Dubai on the way to Europe are now travelling via Incheon, the airport corporation said, fuelling an 18% rise in transfer passengers from the same period last year.

The number of transfer passengers whose final destinations were in Europe rose 63.2% to 210,000, it added.

The corporation said the expansion of infrastructure also enabled the airport to manage a larger traffic load. Incheon, which opened in 2001, serves 158 international destinations.

In comparison, Hong Kong's International Airport serves 139 destinations, Shanghai's Pudong serves 92 while Tokyo's Narita serves 86.

"We're grateful for the [South Korean] government's support, the public's encouragement and the hard work of everyone stationed at the airport in making Incheon the world's No. 1 airport," said the Incheon airport corporation's acting president Kim Beom-ho.

Kim added the corporation planned to strengthen competitiveness by focusing on passenger convenience.