Microsoft Flight

While you do not need it, the P51 will make it much easier to gain this achievement. To make it go faster, start a free flight with full fuel over one of the higher points on Hawaii. Open the throttle to full and put the nose of the aircraft in a steady climb so that your speed is constant but your altitude is increasing. Leave your pc alone for 10 min, come back, and you should have the achievement. It is recommended that you do the "Mach 1" achievement straight after completing this one.