In 1959, the busiest airport in the world was Midway, south-west of downtown Chicago. Within three years, the title had moved. But not far — just 25 miles north, to O’Hare airport.

MDW, as it is known, was considered too small for the impending Jet Age. Chicago was the aviation junction for the US, and it needed room to maintain its lead. So Orchard Field, north-west of downtown, was chosen as the location for a mega-hub. It kept the code (ORD) even as it adopted the name O’Hare.

The city fathers chose wisely: OAG, the global purveyor of airline intelligence, has named Chicago O’Hare as the world’s top mega-hub. How is the champion chosen? OAG looks at every arriving flight, and counts the number of “legal” connections within six hours.

With a “connectivity index” of 1,204, O’Hare is way ahead of its nearest competitor, Atlanta. The two airports tussle constantly for title of busiest airport in the world, and the Georgian venue is presently ahead. But for the traveller who wants to maximise their travel options, Illinois is the state to be in.

Working down the list, the Lone Star State is next: Dallas-Fort Worth is third — 10 places higher than its Texas rival, Houston George Bush.

Next come Denver and Charlotte. The top five show that population size isn’t everything for an airport. Neither city, nor Atlanta, comes close to one million people, yet the trio are global hubs.

America’s biggest city, by some measure, is New York — yet the city doesn’t even make it to the top half of the 50 mega-hubs. Newark is 26th, JFK 31st.

Completing the heavyweight half-dozen: Los Angeles (LAX). Yes, the first six mega-hubs are all American.

I would never have guessed the airport in seventh place: Jakarta, the Indonesian capital, from which dozens of domestic flights radiate.

For the rest of the top 10, it’s back to the US: Seattle, San Francisco and Phoenix.

Rank Airport 1 Chicago O'Hare (ORD), US 2 Atlanta Hartsfield-Jackson (ATL), US 3 Dallas-Fort Worth (DFW), US 4 Denver (DEN), US 5 Charlotte Douglas (CLT), US 6 Los Angeles (LAX), US 7 Jakarta Soekarno-Hatta (CGK), Indonesia 8 Seattle-Tacoma (SEA), US 9 San Francisco (SFO), US 10 Phoenix Sky Harbor (PHX), US

The rest of the world gets a look in at 11, in the shape of Haneda — Tokyo’s biggest airport. To find Europe represented, you must wade through Minneapolis-St Paul, Houston and Detroit before you reach number 15.

Heathrow will be please to be placed above the other European hubs, but Britain’s biggest airport is only fractionally ahead of Sydney. Canada waves a flag at 19, in the shape of Toronto, while Frankfurt scrapes into 20th place.

The next decade is a cheerfully multicultural repertoire of key business locations that are also splendid tourist cities: Amsterdam, Delhi, São Paulo, Las Vegas, Mexico City, New York (Newark), Singapore, Mumbai, Paris and Vancouver. Well, you might not be booking instantly for 48 Hours.

You will spot some surprises further down the list — either for their poor placing or for doing remarkably well. Hong Kong, Miami and Istanbul will be disappointed to be down in the 30s, while Melbourne and Bogota are probably pleasantly surprised. Dubai, which handles more international passengers than any other hub, only just scrapes in at 48 — embarrassingly behind Baltimore-Washington, the US capital’s second airport in the table.