Grand Theft Auto V (Xbox One)

Once you complete enough of Trevors story you will gain the ability to purchase properties, and McKenzie Field Hangar was the property that I was outside when this happened so I suspect you will be in a similar position! If not, McKenzie Field Hangar will be marked on your map as a Property for purchase so just set a waypoint and head there.
You will need $150,000 to buy the field and once you have done so, there's a cutscene where you meet the Control Tower operator Carlos.

Carlos will now inform you that there is an ongoing arms trade 'war' going on, so you will be required to either use the dune buggy provided to carry out weapons drop collections (travel to a set location, sometimes racing against rival gunrunners and sometimes staying offroad to avoid the police) or using the plane provided to either drop weapons or bombs on customers (or rivals). Once you have completed 5 of each type of mission, the achievement will unlock.

Each time you complete a plane or dunebuggy mission, you may need to drive away from the area for a short while so the next job(s) can 'spawn' but it's possible to do 5 of each without having to do any side missions or main missions in between.

*EDIT* Capt Stanners has pointed out in the comments that, to save time, instead of driving away to get the jobs to respawn, you can simply QuickSave from your in-game phone, the reload the save and the jobs will have respawned. Not tried it myself, but once saved you won't have lost any progress so nothing to lose! :)

*EDIT pt.2* I mistakenly mentioned that the 5 flights and 5 dune-buggy missions count towards your 100% stat in the comments - as pointed out by a few, that's NOT the case, but Rockstar Social Club site will actually track how many of the 5 required that you've done.

Secondly, in order to keep this solution spoiler-free, I won't go into too much detail but Kawwaah Kawwaah has pointed out in the comments that the last mission of the single-player campaign may affect your ability to complete this achievement so best complete the requirements for this achievement BEFORE you begin the big (UD) final heist. Just sayin'. toast

(Credit goes to Oh Jay Arr)

First, you need to purchase the McKenzie Field Hangar. It is available after the mission Nervous Ron, for a cost of $150,000. It can only be purchased by Trevor.

Once you purchase it, two icons will appear near the hangar: a plane and a dune buggy. Getting in the relevant vehicle will begin the mission. There are five of each to complete. Once you complete one of each mission back-to-back, you will have to wait for both to respawn, so drive a short distance away to trigger the next mission in each chain. Alternatively, if you fail a mission, the other type will spawn when you return to the hangar.

Depending on choices at the end of the game, there is the chance that you will not be able to unlock this achievement. To avoid this, choose Option C at the end of the game.

Air Missions
In each of these, you will have a limited number of arms packages or bombs to drop on targets, so ensure you are as accurate as possible. You will have some spares if you do miss a target.

1) There are two drop-off locations. Simply fly to each, and press to drop the cargo in the marked zone. Then fly back and taxi into the hangar.
2) Much the same as the first one; only difference is that there are three drop-points. There is also an altitude restriction, meaning you must remain below the limit marked on the radar.
3) For this one, there are four targets. This time however, you much drop a bomb at the location. The mechanic is the same, press when over the zone marked on the mini-map. Be careful with the eastern-most one. There is a tree that can be hidden by smoke that I managed to crash into. When dropping the bombs, you have a small amount of control over the bomb, so make use of this.
4) There are only two targets this time; one is a moving train. Fly above it in the same direction the train is travelling, and when you are close to the front, drop the bomb. As long as you are reasonably close you should hit it. The other target is a group of boats. Drop the bomb roughly in the centre of the cluster and they should all blow up.
5) For the final air mission, you must carpet bomb several vehicles. They are all marked on your mini-map, and are grouped in three clusters. Fly relatively low, and line up your plane with a line of vehicles before releasing the bombs. Hopefully you will get all three with one drop; if not, line up and try again. Be warned you have limited supply of bombs.

Ground Missions
These require you to drive to a location and pick up a package. Try to stay off the main roads as much as possible, or the cops will begin chasing you. When you get tot the package, you don't have to get out of the car, simply driving over it will pick it up. If you are quick, you may have to wait a few seconds for the package to drop; if not then your rivals will be close by and may steal the package. If so, kill or out-drive them to complete the mission.

1) First you have to drive to Maude's mobile home, just south of the airfield. Pick up the package and deal with any rivals that appear. Drive back to the airfield to complete it.
2) For this, you must drive to some docks nearby. Chances are, for this one the rivals will beat you. Get after them and either shoot them out of the car, or blow them up with a sticky bomb before returning to the hangar.
3) You have plenty of time to get this one if you drive off-road. Head to the farmhouse to the north, grab the package and drive back. Chances are, you won't see the runners at all on this mission.
4) Head to the location, where you will likely find the rival runners have already got the package. Kill them all or to make them drop the package, pick it up and head back to the hangar.
5) For the final mission, you have 1:38 to get to the location. Once there, you will be ambushed so either kill them all or drive away. On the way back, you will likely be attacked by a helicopter. Get out of your dune buggy and shoot out the pilot or use an RPG. Then return to the hangar.

Completing all 10 of these missions will unlock the achievement, and they should spawn in the order listed above.

The videos below provide a visual aid for completing these missions should you prefer. It was capture on the Xbox 360 version of the game, but the missions are identical.