If you try to control Microsoft Flight Simulator 2020 with the SendInput API, you may find that the key presses do not register. This is because they must have a non-zero duration. Insert a delay between the key down and the KEYEVENTF_KEYUP event. The same goes for mouse clicks - there must be a delay between MOUSEEVENTF_LEFTDOWN and MOUSEEVENTF_LEFTUP.
For the exact delay, note that a fast typist will do 10 presses per second (an average typist managing about 3-4), and professional gamers can do 10-12 mouse clicks per second (with average gamers capable of 6-7)[a], so delivering the input events with 100 ms delay between them would be approximately pro-level human equivalent.