Insane AirG 20

Ok, here we go:

First of all start up CARNAGE MODE, then chose the very first race Water Canal 1.

Pick the default car that is being offered.

Now onto the actual race:

From the start fall back bit so you won't get bothered by the AI cars. Race through the aquaduct as you normally would in a type of game like this. Jumps give you Nitro which you need to save up for now. You will pass through 3 checkpoints (banners across the street).

Shortly after passing the 3rd checkpoint keep to the left hand side of the road (do NOT enter the shortcut on the right hand side of the road) and you will see a ramp / jump. It's really hard to miss. It leads to the top of the buildings on the left side of the road.

Approach the ramp from as far left as you can and drive on it so you would exit it on the top right side. Just before you leave the ramp press Ctrl on the keyboard and you'll use your Nitro. This will result in a powerfull jump.

If all goes well you'll catch quite some airtime because of the jump and the subsequent drop onto the street (you'll have passed through the gap in the rail on top of the buildings).

It may take a few tries but this is the first opportunity you'll get to obtain this achievement.
If you fail, press ESC on your keyboard and choose to start over the race.