Most people know it, some stopped playing different game worlds because of this;
Every game-world switch takes a lot of clicks. And if you play more than two game worlds (or have a small monitor), you have to scroll. This not only takes a lot of time, it becomes annoying.
So my idea has two parts, the first one is more important (in my opinion), the second one is luxury
If you log in you have some control panels at the left side. (screenshot)
In this (at the bottom or in the middle above the "My Account"-section, red lines in the screenshot) could be some links implemented, that lead you directly into the other game world - in the same window. So if you are at the "My Aircraft"-page in ATB game and use the shortlink, you will instantly see the "My Aircraft"-page of Modern Times #2.
There should no affirmation pop-ups etc. (or make this optional in the settings) to make sure it's a one-click-feature.
This feature allows people to fast-check all of their airlines.
You not only have a fast-switching possibility, you also have a "command room" for all of your airlines. All messages are shown. You're logged in at Alliance Challenge and the FAA will close some of your routes in Jet Age? No problem! The message from Jet Age will also appear there and you can fast-switch to find a solution.
Also the current ingame times of all game worlds will be shown. You know the clocks at airports? Time at Paris, London, Dubai, New York and Los Angeles? There you can see the time of your Jet Age game, Modern Times, Alliance Challenge and Beginners World.
I'm sure there could be implemented more cool things, but these two are some I often miss... hope others will add features they miss.