Crackdown

This solution should work, too... But doing "XI YEMETH IX" solution is more fun though ;)...

Video description: A video showing the easiest way to achieve the "Hazardous Hangtime" achievement in Crackdown. You will need 4 stars in driving in order to use the Agency SUV's special.

Note:Achievement did not unlock for me because I have already unlocked it

I have a solution so easy that you don't even have to leave the agency!

Its a glitch that you can use. Still works as of August 2013.

Before you get this achievement, make sure you have a 4 star driving skill because you will need the jump upgrade for the agency SUV.

First things first, get the agency SUV from the garage. Stay in the garage with the SUV. Now use the jump upgrade. Just hold down B then let go to jump. Now once your flipped over MAKE SURE your on the platform that you got the SUV from. Now just wait for 6 seconds then flip back over.

Achievement is yours.

Maximise your driving skill and ride in the agency SUV. It should have the ability to bunny hop by pressing 'B'.

Go to downtown shai-gen. Go to the tallest building, there is an elevator inside you can take to the top. One of the bosses is found at the top so you should know which building it is, impossible to miss.

Take your SUV in the elevator. Activate the lift to the top. Climb your way past several floors of ramps until you reach a balconey looking over the plaza. Build some speed, hold 'B' and let go of 'B' before the ledge. You should remain in midair for 6 seconds or more gauranteed. When you land, you will get the achievement.

I got this one unexpectedly while I was actually trying for a different achievement. Hopefully it will work for you as well.

Get the SUV from the Agency and go through tunnel #2 to the Volk area of the city. Just to the east of where you come out is an open mall type area with several large pillars in a line along the beach. There is always a ramp truck parked toward the north end of this area.

Leave the ramp truck where it is and get out of the SUV. Pick up all of the trash cans and benches along the sidewalk running along the beach and throw them in the water as they will deflect your vehicle.

Now get back in the SUV. Start at the south end of the side walk and head north, building up as much speed as you can. Hold down the "B" button before you get to the ramp truck and let it go just as you leave the ramp. You should be aiming your vehicle just to the right of the building straight ahead.

You will sail past the building and land on the beach down below, and the achievement should pop when you land. If you don't get it, there are some stairs right there that you can drive up to get back to the mall area.

PS - I don't know if it makes any difference, but I did not do any flips or barrel rolls when I got. I was going for a long jump.