Microsoft Flight Simulator is set to take to the skies in it's first closed beta in Mid-July, according to the latest development roadmap posted last week.
The game has seen various alpha versions tested by select insiders since October of last year, with regular alpha testing currently ongoing. There are a few more alpha tests scheduled before the beta test in June, but will likely open up to more insiders, so it's worth signing up now for a chance to be included.
The game is due to release this year and is one of the most ambitious projects in video gaming I have ever seen. It utilizes Bing maps and telemetry data to create a perfect representation of the entire Earth, right down to every building, every bridge, even your own house. Machine learning takes map data from Bing and uses it to build a full 3D representation of Earth, including all 1.5 trillion trees (yes, there are that many trees, more than the number of stars in our galaxy, apparently.)
Like many Microsoft Insider programs such as the Windows, Xbox, and Halo insider programs, anyone can sign up to take part. However, you will only be selected to be included in certain flights (if you pardon the pun) either at random or based on your hardware. Later more general test versions become available to all insiders.
You can sign up for the Insider Program here.