I recently came up with an idea to compete better against other airlines in the first years, or when moving to a new country in a no political restrictions world: Make your hub/HQ in an airport that has high amounts of traffic but has short runways.
I've realised that most people don't fly to those very much and they rarely place hubs in there, while the biggest airports of some countries are sometimes the HQ of 4 airlines and hub of 6, and the competition there is terrible. So I've been trying to open hubs in these with airplanes that meet the runway requirements, and once I have a decent profit I can start trying to compete against the other airlines for the bigger airports
So, I'm trying to make a list with some airports with a considerable amount of passengers but with short runways. Preferably if there's another bigger airport with longer runways on the same country, but not neccesary. If you guys know about some please tell me
USA: Chicago Midway (MDW) and New York La Guardia (LGA) have a lot of passengers (around 20mil annual IIRC) and of course there's lots of bigger airports in the US. There might be more but I haven't checked if they have decent amount of passengers
Ireland: Dublin Airport (DUB) has lots of passengers and is the largest of its country. It's runway is not THAT short (~8600ft), but it is still enough to keep some competitors away, specially during the 50s, or the early jet age when some planes have >9000ft runway requirement
Brazil: Sao Paulo Cogonhas (CGH) is Sao Paulo's secondary airport but it is still one of the biggest in South America. Lots of competition for regional/domestic flights but not so much for international long-haul ones. There's also Rio de Janeiro - Santos Dumont (SDU), but it has a terribly short runway (4300ft) so I doubt you can use many planes there. There's big airports in Brazil to expand to later (GRU, BSB, GIG)
Argentina: Aeroparque Jorge Newbery (AEP) has ~10mil annual passengers and a runway just below 7000ft. It is the biggest airport of the country so there is some competition, but there's also Ezeiza (EZE) that has ~8mil annual passengers and a long runway