The latest game world at AirwaySim has just started a few minutes ago. This world, named Dawn of the Millennium, takes the player to the 1980s and 1990s with rapidly growing air travel demands and the world of many changes.
This game world lasts about 5,5 months when played from the very start to finish line and it includes the (standard) ability to open multiple base airports within each airline's home country, and also various twists in economics and fuel prices.
With this scenario the available "main" game worlds include the three major time periods, early (1960+), near past (1980+) and modern (2000+). The other two worlds, Modern Times and Jet Age, are currently full but keep an eye for open spots on them too!
https://www.airwaysim.com/game/