The mission entitled 'Dust Off' is actually very simple. I normally put on a nice mood soundtrack, say the 1971 Dirty Harry movie score and do the following. After leaving U.L. Paper's office in the Federal building drive to the initial starting point and then park up as directed. Once you see the cut-scene with the helicopter, give immediate chase - driving down the turnpike as fast as possible. If possible keep the copter in sight, but if you cannot do that keep track of its position on the radar. The copter will fly an atypical course down along the southeastern side of Algonquin, and will weave out over the river before heading back in among the buildings - IGNORE this and just concentrate on driving. Your immediate goal is to get as far south of the island as possible on whatever highway you choose to use (without entering the gardens at the southern end). When you see the highway make a sharp right turn follow it and carry on up the main turnpike to a point roughly mid-way up the Algonquin island, wherein you will see on your immediate left a large multi-story parking lot jutting out into the West River. Make an immediate hard left BEFORE the structure I just mentioned and you will see a ramp leading down to a structure out on twin booms in the river. But be advised that as you approach, slow down so you can ice the two guys on guard duty there.
Killing them will not cause the game to default, so you can ignore them if you wish ... then continue on down the nearest ramp and pull to a stop close by the landing pad which the helicopter will have settled down into by now. Be careful as you pull to a stop as a bunch of gangsters are standing there close by some crates and drums and are armed. If possible use the car for some cover and take them out. Once they are dead, go to the helicopter and board it. As you rise up into the air a lone gangster will run from concealment and grab one of the landing skids and hang on tight. If you are feeling sadistic, scrape him off by flying low enough to slam him into the building - but watch your blades! Failing that, simply perform some maneuvers and he will eventually lose his grip and fall to his death. After this it is simply a case of flying out across the city, avoiding slamming into any buildings and then to Francis International Airport where you should land on an open area of flat slab close by the radar tower and an enclosed loading dock area. DO NOT land IN the loading dock, instead just beyond it. To land successfully slow and descend - if necessary carefully flying backwards (direction) while decelerating to come in nice and soft.
As soon as you have settled down a couple of F.I.B. personnel will appear and take care of the copter and you can leave the airport using a car parked up nearby. Be sure to use the nearest gate to leave or you may trigger an All-Points alert as a trespasser on airport property. My 'simple' solution for Paper Trail is also in the forums, go take a look - everything will be simple afterwards.
Go get 'em tiger!