Heathrow passenger numbers declined by 1.2% in October as the airport won approval for a third runway.
The drop was partly blamed on flight cancellations stemming from Hurricane Matthew in the US.
The London hub handled almost 6.5 million travellers in the month with emerging markets showing the strongest growth.
Mexico was up by 9.4%, East Asia by 2.8% and India by 2.1%.
This provided evidence that demand to fly from the UK’s “front door” remains strong, the airport claimed.
Larger, quieter and more efficient aircraft continued to be a driver for growth in passenger numbers which are up 0.5% in the year-to-date as airlines deploy more and more new generation Airbus A380s, A350s and Boeing 787s at Heathrow.
Heathrow chief executive John Holland-Kaye said: “In October, the prime minister sent a clear message to the world that her government would expand Heathrow, showing that Britain is open for business and confident in its future.
“With the support of communities across the UK, Heathrow is now working at pace to deliver the benefits of Britain’s new runway – an affordable plan that creates more jobs, boosts exporters and builds an economy that is stronger and fairer for everyone – as quickly as possible.”