The importance of Heathrow as a major international airport was emphasised today by a passenger survey from the Civil Aviation Authority (CAA).
It showed that in 2010 as many as 58% of passengers using Heathrow were foreign residents.
Four years ago - in 2007 - the proportion of overseas passengers at the west London airport was 55% and has grown each year since.
Last year, 36% of passengers using Heathrow were connecting passengers - a decrease on the 2009 figure of 38% but higher than the 2008 figure of 35% and also higher than the 2007 figure of 34%.
The Government has ruled out a third runway at Heathrow - a policy that has been called into question by airlines and Heathrow operator BAA.
Those pressing for Heathrow expansion argue that the west London airport is an important international hub and that Britain will lose out economically to European rivals if an already-busy Heathrow is not allowed to grow.
The CAA figures were based on responses from more than 200,000 departing air passengers about their travel patterns in 2010 at five London airports - Heathrow, Gatwick, Stansted, Luton and London City - and seven regional airports - Birmingham, Doncaster, Humberside, Leeds Bradford, Liverpool, Manchester and East Midlands.
A total of 51% of the passengers at London City airport were foreign residents.
In contrast to Heathrow, fewer than 1% of passengers at Doncaster, East Midlands, Humberside and Leeds Bradford airports were changing planes.
London City was the most business-centric airport in the study, with 63% of its passengers travelling for business purposes, returning almost to the airport's pre-recession 2006 level and representing a 7% improvement on 2009.
The next highest were Humberside with 32% and Heathrow with 30%, while the airports with the highest proportion of leisure passengers were Doncaster with 97% and East Midlands with 92%.
Passenger income in general continued to grow when measured at those airports surveyed in 2008, 2009 and 2010. For instance at Heathrow, the average leisure passenger's household income increased by £2,000 to £60,000 and at Manchester the average business traveller's income rose from £65,000 to £68,000.
Average leisure passenger household income dropped slightly at both Gatwick and Luton airports.
Travellers from Heathrow took a higher proportion of trips over two weeks in length than anywhere else, at 23%. In contrast, London City had the lowest proportion at only 2%.
Outside London, the highest proportion of trips over two weeks was recorded at Humberside, with 18%. The lowest was at East Midlands at 6%.
CAA regulatory policy director Iain Osborne said: "We survey people using UK airports to make sure that we understand how and why people travel by air to make sure that our regulation is tailored to their needs.
"This year's results will inform our response to the Government's work to develop an aviation policy framework - with information about how passengers use the country's major airports particularly relevant to Government."