Some 10 or 15 years ago I tested the x-Plane 15 minutes demo. I considered it a bit limited. However it had the option of flying at Mars, which was rather challenging, not to say impossible.
The reason it is so challenging is the combination of less gravity and thinner atmosphere (about 30% and 1% of the Earth's). That means huge wingspan and incredibly high stall speed, however if you dare turn your aircraft you have to consider that you have to use that thin air to change the flight direction while you due to the weight and speed of the aircraft both are huge. Also remember that you needed a third of the lift due to the lower gravity, but that it also means that you have one third of the agility, if I'm not mistaken (please correct me if I'm wrong).
The bigger challenge I guess (since I rarely got that far) is the landings. Manoeuvring in is one thing, stopping is a completely different. Airbrakes - not usable, too thin air; reversers - not usable, too thin air; wheel brakes - hardly usable, to little gravity, arresting gear - oh yes.
I think I read about Austin Meyers attempts at flying on Mars here: The Martian Chronicles (February 2000, experience not real: Simulated in X-Plane only).