Heathrow experienced its busiest day on record last month, the airport announced.
Some 262,000 passengers travelled through the west London hub on August 4 as many people set off or returned from their summer holidays.
A total of 7.7 million passengers flew to or from the airport during the month as a whole, up 0.1% on August 2018.
Africa was the region with the largest year-on-year percentage growth in passengers numbers, with a 6.0% increase fuelled by a new Durban route and larger aircraft on Nigeria flights.
Demand for domestic Heathrow flights was up 2.7% as more passengers used services to and from Newquay, Guernsey and the Isle of Man during the peak season for UK breaks.
Earlier this year, the airport announced it is investing £50 million to roll out computer tomography (CT) equipment which could enable passengers to keep liquids and laptops inside their hand luggage when passing through security.
Heathrow chief executive John Holland-Kaye said: “We are continuing to invest in future proofing Heathrow.
“The airport will be a test bed for ground-breaking technology like our new CT scanners to ensure that our passenger experience remains world class as numbers continue to grow.
“Using new technology and innovation as we deliver expansion will also demonstrate our global leadership on sustainable travel.”
Aer Lingus fly direct to the West London airport from Cork, Shannon and Dublin