Microsoft Flight Simulator launched for PC back in August last year, and it is a demanding beast that has gotten even the most powerful computers to cry. This might be one of the reasons why the Xbox Series S/X version hasn't launched earlier, but it's planned to be released this summer.
Unfortunately, games these days tend to be really delayed, so will Microsoft Flight Simulator be released as planned? It actually seems that way, as the game has now been age rated by PEGI for Xbox One. This is interesting as the Xbox One version hasn't been announced yet.
If it isn't a mistake, it does seem like we might get two versions of the game this summer for both Xbox One and Xbox Series S/X, and that delays likely will be avoided.