Gatwick Airport has landed a blow on Heathrow in the bid to win the recommendation of the Airports Commission for a new runway after reporting almost 6% passenger growth in the last year.
The Sussex airport welcomed 5.8% more passengers in May compared to the same month last year while Heathrow recorded just 1.7% growth.
In the final set of traffic figures before the Sir Howard Davies' commission is expected to suggest which airport should be expanded, Gatwick announced that 3.6m passengers travelled through the airport last month. It is the 27th consecutive month of growth the airport has shown and has been driven by the increase in trans-Atlantic flights.
Heathrow meanwhile reported a record breaking May with 6.34m passengers travelling through the west London hub.
It also set new single-day passenger records for arrivals (131,327 on 31 May), departures (129,059 on 22 May) and overall (246,516 on 22 May).
Emerging markets boosted traffic growth with passenger volumes to China up 19.2%, Mexico up 15.9% and Brazil up 11.2%.
Pointing to figures that said Gatwick had grown by 8m passengers a year since the break-up of the BAA monopoly in 2009, airport CEO Stewart Wingate said a rival to Heathrow would improve the whole sector.
"Choosing airport competition over monopoly is the only answer that is right for the whole of the UK," he said.
"Expanding Gatwick would enhance competition, meaning Gatwick grows, Heathrow improves, and every part of the UK benefits from a stronger network of competing airports providing passengers more choice, higher standards and lower fares."
His Heathrow counterpart, John Holland-Kaye said the growth in passengers and exports to emerging markets shows how "only Heathrow expansion will keep Britain at the heart of the global economy."
The Airports Commission is presiding over which airport is best placed to develop a new runway in a bid to boost the country's aviation capacity.
Gatwick wants to build a second runway while Heathrow has put forward plans for a third runway to the north-west of the airport and an extended northern runway.