London's Heathrow Airport, which is battling Gatwick for government approval for an extra runway, said it handled a record 7.34mn passengers in August, with more flying to the Middle East and Latin America.
Heathrow operates at about 98% capacity and struggles to add new flights. The British government is expected to rule in the coming weeks on whether to build a third runway at Heathrow or its rival Gatwick after a drawn-out process.
Europe's busiest airport said numbers grew by 0.1% on the previous year, showing there was no dip in traffic following Britain's June vote to leave the European Union.
Heathrow has argued that Britain's vote to leave the EU makes it more important that it secures approval to expand, enabling it to build more routes with trading nations. Gatwick says it can build a new runway at a lower cost and with less environmental impact.
Heathrow said passenger traffic rose by 9.1% to the Middle East, by 5.8% to Latin America and 5.1% to East Asia year-on-year in August, helped by increased use of larger aircraft.
Passenger growth to these countries outweighed falls on internal flights in Britain and to North America and Africa.
The airport, whose biggest shareholder is Spanish infrastructure firm Ferrovial, said passenger volumes were up 0.7% in the first eight months of 2016, compared to the same period in the previous year.
It said cargo traffic to emerging markets also rose, by 5.7% to the Middle East, 12% to Latin America and 3.7% to East Asia, supporting its case for a new runway.
"We can get exporters, large and small, from all across Britain connected to the growing markets of the world, and it is urgent that we get on with it," Heathrow CEO John Holland-Kaye said in a statement.
The decision has repeatedly been delayed over pollution concerns and local opposition.
Heathrow's figures come after Dubai International Airport, the world's busiest for international travel, said last week that passenger traffic jumped 14% from a year earlier to a monthly record of 7.62mn people in July.
Growing tourism and trade ties with the rest of the Middle East, Asia and other regions of the world are fuelling traffic growth at Dubai's airport.