"Microsoft is not allowing cross-play completely; which means [War Thunder] cannot be on Xbox One," Yudintsev told GameSpot. He explained that Microsoft requires a certification of game servers to guarantee a positive experience for players, a goal that Yudintsev says "isn't possible under the current circumstances."
He added that Microsoft has a lot of "unspoken limitations" for free-to-play games, including a system of approval that's more based on whether the project's account manager likes the game, rather than a general set of rules. In contrast, Yudintsev stated that Sony is more open to free-to-play games, adding that the PS4 version of War Thunder is expected to support cross-play as early as next month.
Microsoft responded to the story, stating that it works with developers interested in supporting cross-play between the Xbox One and PC to "ensure a great user experience." On the upside, Yudintsev complimented Microsoft's ID@Xbox initiative, adding that he hopes Microsoft's changing policies for indie games will allow Gaijin to eventually launch War Thunder on Xbox One.
Update: This article has been corrected to reflect War Thunder's proper developer, Gaijin Entertainment rather than Gaijin Games.