The demo allows you to fly for roughly 15 to 20 minutes before the joystick controls are disabled. However, you can restart the demo as many times as you want.
X-Plane 12 uses an internet-based activation system. Each key is unique and linked to a specific user account or hardware ID. Once a key is used and registered, it cannot be reused by another person. x plane 12 product key free link
Occasionally, Laminar Research offers discounts when purchasing the sim alongside specific hardware or add-ons. The demo allows you to fly for roughly
Serial numbers found on forums or "paste" sites are almost always blacklisted by Laminar Research within hours. How to Play X-Plane 12 for Free (Legally) x plane 12 product key free link