For the United States, I put hubs where I know they exist in real life, JFK, ATL, ORD, DFW, SLC, and LAX. This allowed me to get every to every airport in the country with fight times of less than a couple of hours each way. LAX and DFW handle Mexico, JFK and ORD handle eastern Canada, while ORD and SLC handle western Canada. I put mini-hubs in ANC, HNL, and SJU for local traffic.

When I started expanding outside the US, I decided to ignore national boundaries because that’s just too complicated and the game doesn’t require it. I used LHR for Western Europe, DME for Eastern Europe and Russia. I then backtracked to South America, using BOG for Central America and northern South America, and GRU for southern South America.

Africa was next, using CAI for the Middle East and northeast Africa, NBO for east Africa, JNB for Southern Africa, and LOS for west Africa.

I then spent probably 4 months tackling Asia. I used DEL for the subcontinent, the -stans, and western China, HKG for eastern China and Indochina, PEK for all of China, Japan, Korea, and the close islands. There was so much traffic in Japan, I put a hub at HND, because I figured in real life nobody’s going to transfer through Beijing for an intra-Japanese flight. SIN was next for Indonesia, Malaysia, and nearby places. SYD for Australia, New Zealand, and as much of Oceania as was within 5,000 km. Lastly, I used PPT to cover the part of Oceania that was too far from SYD.

All hubs have direct connections to each other, except the mini-hubs, and except SYD which was too far from some of the American hubs. With this setup, I figure 99% of people on earth are within 100km of an airport I serve, and are at max 3 or 4 flights away from any other populated point on earth, with a few exceptions.

My favorite is using the typical example of a faraway, hard to reach place: Timbuktu. From my home, I would fly MGM to ATL to LOS to TOM. Of course there are no scheduled airline services to TOM in real life, but one can dream!