Luckily you don't have to have something flying upwards for 5 grid units.

On Bridge 3 of the first island, build a ramp up from the left side (by having the first piece of road at a slope of 1, the second at a slope of 2, the third at a slope of three, and the fourth at a slope of 4) and support this with various triangles of wood. Then play the level, and choose the cars. As the first one flies off the top of the ramp, you should get the achievement.

On Bridge 3 of the first island, build a ramp up from the left side (by having the first piece of road at a slope of 1, the second at a slope of 2, the third at a slope of three, and the fourth at a slope of 4) and support this with various triangles of wood. Then play the level, and choose the cars. As the first one flies off the top of the ramp, you should get the achievement.