Passengers transferring from one flight to another account for more than a third of all travellers passing through Heathrow, according to a study by the government’s air transport adviser.
The importance of the role that connecting passengers play at the UK’s busiest airport has long been a source of conflict among campaigners for and against a third runway.
Released on the eve of a Commons debate on the proposed expansion, the finding may fuel growing criticism at Westminster.
The aviation industry – led by BAA, the airports group, and British Airways, the biggest operator at Heathrow – claims that transfer passengers are crucial to the economics and competitiveness of a hub airport.
Without them the scale of the network and range of destinations as well as the number of daily services that can be supported on routes would suffer, damaging Heathrow’s attractiveness compared to European rivals such as Paris Charles de Gaulle, Frankfurt and Amsterdam Schiphol.
But opponents claim reducing the volume of transfer passengers would relieve pressure to expand Heathrow, greatly undermining the case for a third runway.
The CAA report underlined the role that London plays as the country’s aviation hub with 90 per cent of connecting air passengers in the UK using the three main London airports. Heathrow alone accounted for 70 per cent of all connections, the majority of which were made by non-UK residents.
The CAA document largely backed the argument that transfer passengers play an important role in supporting the range of services at Heathrow. Its survey evidence suggested connecting passengers helped “to maintain a wide range of flights to different destinations and helped to ensure more frequent flights to popular, often business destinations”.
The report said the share of transfer passengers at Heathrow had grown from 22 per cent of all passengers 20 years ago to a peak of 37 per cent in 2003. It had fallen back slightly to 35.1 per cent in 2007.
Last year just over three-quarters of those transfer passengers were connecting between two international flights, with the remaining 23.9 per cent transferring between domestic and international flights. The CAA statistics count connecting passengers as two passenger movements, once on arrival and once on departure.
The share of passengers transferring between two international flights had grown from 57 per cent to 76.1 per cent in 20 years with the absolute number quadrupling from 4.4m to 17.9m. In the same period total passengers at Heathrow had doubled. In contrast, connecting passengers accounted for 54 per cent of travellers at Frankfurt, 42 per cent at Amsterdam and 32 per cent at Paris Charles de Gaulle.