The results put Gatwick ten years ahead of forecasts from the Airports Commission, with 4.3m passengers passing through the airport in July.
Gatwick chief Stewart Windgate said the results are “further proof of the flaws in the Airports Commission’s analysis and shows its conclusions are fast unravelling”.
While both airports reported a record number of passengers last month, Gatwick said that July was its jewel in the crown, marking two and a half years of consistent growth.
Stansted has also seen year-on-year growth. While footfall in July rose 12.5 per cent compared with last year, total passengers flying from Stansted increased by 16.5 per cent.
Stansted said that last month saw the best July traffic for seven years.
Gatwick Airport said an increase in long-haul flights has made a huge contribution to its growth. While long haul flights were up by more than 12 per cent this year, flights to New York and Los Angeles both rose by over 100 per cent.
In response to the Gatwick chief, an Airports Comission spokesperson said forecasts “were subject to extensive analysis and we are confident that they are fit for purpose”.