August was the busiest month on record for both Gatwick and Manchester airports.
At Gatwick, more than 4.53 million passengers passed through, a 3.7% rise on the same month in 2014 and the 30th month of consecutive growth.
A total of 39.5 million passengers have been handled in the last 12 month, up 6% year-on-year.
Gatwick chief executive Stewart Wingate said: "Airports Commission analysis predicted Gatwick would reach 40 million annual passengers in 2024 yet, in August 2015, we reached the 39.5 million passengers mark.
"We are in touching distance of 40 million and on track to reach this milestone within a matter of weeks.
"This is more evidence of the flaws in the Airports Commission and we will continue to make our case to government as it approaches a decision. Gatwick remains the best and most deliverable option to actually deliver the runway that the UK needs."
Meanwhile, a record-breaking 2,688,133 people travelled through Manchester Airport, up 5.05% on the number of passengers who flew during the same month last year.
This made August the busiest month and this summer the busiest in the airport’s 77-year history.
With figures for 2015 so far reaching 22,750,477, the airport said it was well on track to break the 23 million barrier by the end of the year.
Meanwhile, London Luton Airport enjoyed a record summer with 2.6 million passengers travelling through the airport in July and August.
Last month 1.4 million passengers used the airport, a 16% increase compared to the same period last year, marking 17 months of consecutive growth.
