Crackdown 2

For this achievement i keep hearing people say it has to over all seven islands which is wrong. All you have to do is fly over the three main areas from the first game. Los muertos, shi gen, and volk. You do not need to fly over agency island trust me i have done this several times and with a bunch of people.
The shortest route is to start from the very end of volk, fly through shi gen and into los muertos, i have a picture of the route ill upload. Technically your route can be even shorter than the one shown in the picture but i have heard of bugs where the achievement did not unlock for the super short route if it doesnt work for you just take the longer route shown in the picture. This route works for both City Glider and the Squad City Glider achievement. I took a helicopter to the start location on the map and jumped out from there. Make sure the helicopter is traveling upwards before you jump out or you will kill yourself like I did many times

This requires your agility to be at max (lvl 5) once you do that you'll unlock the Wingsuit (press Y to deploy). Use the helicopter to gain as much height as you can then follow the video for shortest route.

*Video by SK8B0AD3R

For this achievement you need to use your wingsuit to glide over each of the islands, now you don't need to fly over each of the separate islands, you only need to fly through the airspace of the main islands.

Once you max out your agility you'll unlock the wingsuit, to use the wingsuit you need to jump from a decent height and tap the "Y" button, hold down on the "LS" until the lines coming from your agent turn red at this point pull up on the "LS" and your agent will climb in altitude a bit, repeating this process you can glide around the entire game and keep an eye on the mean streets of Pacific City. It's a good idea to have a basic understanding of how the wingsuit operates, the last thing you want to do when going for this achievement is to smash into the water and have to start again!

Right, so there's a lot of debate over what is the best route to take, when it comes down to it, it really doesn't matter which route you take as they all result in you unlocking the achievement, personally I used a chopper to reach the top of the enormous building on the old Shai Gen island, travelled directly forward toward the Agency Tower, veered to the right and flew above the docks of the old Los Muertos island and finally followed the bridge to the old Volk island. I only use this route out of habit though, it's the first route I used.

However, as I stated the route isn't important, you just need to glide through the airspace of the 3 main islands, an example of this can be seen in the video below.

* ^{Credit to XCVii007r1 for the video}

For this achievement you don't need to glide over every island as some places state. You just need to enter the airspace of each section of the map without touching down.

A key component is maintaining altitude while gliding. Do this by pressing up on the left stick until your contrails turn red. When they do pull back on the joystick to gain a little altitude and level out. Do this the duration of your glide.

To get it I grabbed a helicopter and headed to the east coast of the north island of Green Bay. I was about halfway up the coast. I alighted from the helicopter and activated my wing suit. From there I flew over the southwest tip of Unity Heights, then over Agency Island, and then into Hope Springs airspace. (Agency Island isn't needed for the achievement, it just happens to be in the flight path I took to simplify it and just go in a straight line.)

This popped the achievement for me. Once you get used to the wingsuit it should be easy.

Using the thrusters to regain altitude during your glide DOES work - I just watched my brother get the achievement using this method.

I don't know if this also works for but we plan to try this achievement with two friends in the near future so if it does I'll add a solution to that achievement too.