No, it's the way it is in the actual game too.
All your planes must start from your base. However, you can create "W-shaped" routes (even in the demo, which is 100% fully-featured). Meaning that, say you want to fly from Chicago to New York, but you're in Dallas. You can fly from Dallas to Chicago then to New York and back. Or vice versa. But your planes must start all their routes at your Base.
Again, this is due to change in the near future. But it will be limited. How limited hasn't been decided/revealed yet. But you won't be able to start aircraft from any city you want whenever you want, there'll be limits on how many you can have (probably only 1, maybe 2, additional) and there will be a significant cost involved in setting up a new hub.