Elite units are the highest level unit in the research tree.
For example with planes here:
Anyone can research level 6 interceptors.
Once you have level 6 interceptors researched in a game you need to have the blueprints on hand before you can start the research for level 7.
So you still have to research level 7 in each game once it unlocks on the correct day and you have completed the prior research.
Once you collect the required blueprints to unlock an elite level unit you may research that unit in any game once the other prerequisites are met, such as day for that to unlock and the prior level of research is complete.
