If you are like me, then you have backed Star Citizen, have access to Arena Commander but do not have a ship that is ready for the mode (In my case, it is the Freelancer DUR).
Cloud Imperium Games have announced that all backers will have access to the Origin M50 for the next week, bringing its speed and nimbleness which makes it a good choice for racing. There is no need to do anything other than to log into the Hangar Client, select Arena Commander from the menu and get flying.
