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To get the 6,000 distance a little tip is to have everything maxed out, and on the last ramp soon a you fly off use all your boost to achieve a really high altitude and then what you want to do from there is tilt down until your velocity meter is at 175 and you're going to want to keep it there. Once you hit an altitude of like 20, do a dip and get some more altitude and do it over BUT not at a velocity of 175, but a velocity of like 150. Then boom! You got the achievement. ~BigIcy
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When attempting to get 6000 distance, glide up and down to balance out speed and altitude. First dive slightly down to buildup speed, then fly a little bit up (about 2%-15% resistance) to gain altitude. When you fly upwards and gain altitude, you lose speed due to air resistance, so you must dive to gain speed. Save your rocket fuel for later on, and use some of it when you are going upwards to increase altitude. Keep repeating this cycle between diving and flying upwards to achieve minimal speed/altitude loss.