That is completely normal in CMRT. As you already noticed Battlefront walked another route for this game and don´t give you the ability to call in precise air attacks. Why they did that I don´t know anymore honestly but I think it is stated somewhere in the BFC forums.
And if you ask me they should have went the same with the other ww2 games just for continuity. And I know that british and american communication and direction between ground and airforces were pretty good in the later stages of the war. (at least for ww2 ). It would be more in line with the old CMx1 games too.
But to the point: "En route" just means that the plane is under way to the map location, seeking out targets. When it comes is unknown and it is randomly to show up. However you hear it´s engine sounds roughly one minute before it strikes.
I believe the status screen will then read something like "coming around" or "attacking".
The aircraft here is completely on it´s own and can strafe the entire map. That means, depending on it´s experience and luck, it can either attack enemy or friendly forces alike.
