Dubai leapfrogged Heathrow to become the world's busiest airport for international passengers in 2014, the head of the Gulf hub said on Monday.
Dubai International airport dealt with about 71m international passengers in 2014, according to chief executive Paul Griffiths, surpassing the 68.1 million that passed through Heathrow.
"Heathrow is losing a lot of traffic to Dubai because we're able to cater for the connections that Heathrow no longer has the capacity to service," said Mr Griffiths, referring to how the UK's largest airport is operating at near full capacity on its two runways.
Dubai's surpassing of Heathrow comes as the Airports Commission, a body set up by the British government, seeks to reach conclusions on whether to recommend a new runway at Heathrow or Gatwick, the UK's second largest airport.
Both Heathrow and Gatwick on Monday reported record passenger numbers for 2014, and brandished the figures as support for their cases for new capacity.
Heathrow dealt with 73.4 million passengers — a combination of domestic and international travelers — last year, up 1.4 per cent compared with 2013, as additional large aircraft flew into the airport.
Heathrow highlighted strong traffic growth on routes to emerging markets, including China and Mexico.
However, Mr Griffiths, a former head of Gatwick, said that Dubai would continue to grow strongly, adding it was "highly unlikely the UK will regain number one spot for international passengers".
When airport capacity is constrained, companies "start to base headquarters overseas because of cost of travel. It strikes at the core of a country's ability to be competitive", he said.
"Dubai has got them on the run. Now it's ahead, it's ahead to stay there," said David Bentley, analyst at the Center for Aviation.
Dubai International airport's growth is rooted in the expansion of Emirates Airline, the state-controlled carrier that was established in Dubai, part of the United Arab Emirates, in 1985.
Emirates is now operating the world's largest fleet of long-haul passenger jets, and is considering moving to a new, bigger hub in Dubai.
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Heathrow Airport Holdings said the loss of the airport's status as busiest international hub lent weight to its calls for a third runway.
"Britain has benefited from being home to the world's largest port or airport for the last 350 years . . . But lack of capacity at Heathrow means we will shortly lose our crown to Dubai," said John Holland-Kaye, Heathrow's chief executive.
Gatwick dealt with 38.1 million passengers last year, up 7.6 per cent compared with 2013, with strong growth on its core European routes.
"Gatwick's record-breaking figures show an airport serving the widest range of travel and airline models — exactly what is needed from the decision about the UK's next runway," said Nick Dunn, Gatwick's chief financial officer.
Capacity constraints hurt the punctuality of both Heathrow and Gatwick. Heathrow ranked 111th and Gatwick came 139th in a global survey of airport punctuality by OAG, the aviation data provider.
At Heathrow, 75.5 per cent of flights took off within 15 minutes of the scheduled time last year, while Gatwick achieved just 60.1 per cent.