“Secret Flying Simulator is in Development from Valve” is a spam or clickbait headline from a low-quality blog rather than a real product. Valve is not making a game called Secret Flying Simulator, and there is no official or credible announcement about such a project.If you saw this title on a specific website or video, let me know where it came from, and I can help you check if it is a prank, mod, or piece of fake news.