Adelaide Drubman / Friendly Skies
Begin by conquering Drubman Marina, a cultist outpost in the north of Faith's territory and first step in recruiting Adelaide.
This outpost is slightly bugged. To avoid getting stuck in a no-win state, prioritize killing the two schmucks on boat patrol, west of the marina. Start with the pilot
This is key because the guards are linked to the Marina, and this link doesn't fade if they flee out of range, unlike most ground troops. If you're having trouble sniping them yourself, Grace is ideal for laying down the pain here. Just be sure you're in cover first, as it will rile up the rest of the hostiles onshore, including at least one heavy.
After this, standrad tactics apply- snipe from the wooded hill, move often, and use companions to flush out hostiles that have gone to ground in inaccessible places.
Kill them all to complete the location.
You'll see perennial pottymouth Adelaide freed during the liberation cutscene. Speak with her to start the recruitment mission Friendly Skies.
This will give you three locations to search for Adelaide's copter.
Luckily, you don't have to dogfight every suspect. Each location is a helicopter landing spot (or is an overlook of a helicopter landing spot). You can can simply stealth up and ambush the pilot on the ground.
The pilot is a VIP, and there is usually at least one heavy on the ground, so don't just rush in. An easy way to take out the first two sites (with women pilots), is to blow up the helicopter as it lands.
Try to save the lookout site (the southmost goal), for last. This will give the pilot plenty of time to land, so you can kill him without risking the chopper.
When resistance on the ground is dead, climb into the copter and head back to the marina.
You can engage targets of opportunity along the way, but you might skip it unless you have the self-repairing vehicle perk.
When you return to the marina, it's being attacked. It's much easier to land and kill the invaders on foot then to try and take them all from the skies.
There are only half-a-dozen or so hostiles (though NPCs on the ground will account for at least couple on their own). They're mainly clustered by the trucks- kill the rest of them, then talk to Adelaide to unlock her as a companion.