Heathrow airport suffered a 1.8% fall in passenger numbers last month.
The west London airport said 7.2 million passengers passed through its four terminals in June.
That is compared with 7.4 million during the same month last year.
Heathrow attributed the decline to the “continued suppression of Middle East traffic” because of the conflict in the region.
Last month, two million passengers travelled from Heathrow to North America, where the World Cup is being hosted.
That was 1.2% more than in June 2025.
Heathrow chief executive Thomas Woldbye said: “It’s been a strong end to the first half of 2026, despite the challenges presented by the situation in the Middle East.
“Sustained growth in North American and Asia-Pacific coupled with climbing cargo volumes demonstrates the strength of demand for global connectivity.
“As the Government looks for projects that can drive economic growth across the whole of the country, attract investment and create new jobs for young people, Heathrow’s privately funded expansion presents an open goal.
“A third runway will unlock new opportunities for businesses, exporters and communities in every region and nation of the country.
“It’s time to get this vital project off the bench and onto the pitch.”
