Meet Ness at the Crash Site

Meet Ness at the Crash Site is a miscellaneous quest in Fallout 4. This quest is obtained when interacting with Ness during her random encounter.

Quick walkthrough
Ness will hire the Sole Survivor as a mercenary to clear Skylanes Flight 1981 of raiders, offering to split the loot and giving a reward of caps for your cooperation. Multiple Interactions can be performed to increase the amount of "caps" she rewards.

Detailed walkthrough
In a random encounter, a mysterious woman named Ness will ask you to secure a crashed airliner with a secret compartment filled with loot. The only problem is the airliner is populated by raiders. Along with some mercenaries Ness hired, the Sole Survivor will secure the area. Ness and her hired Gunner mercenaries will be located under the right wing of the Skylanes Flight 1981, located a few meters north of the intersecting roads.

After talking to Ness, the player character will get some caps from her. However, the player character can ask Ness what is in the compartment for a speech check. It is then revealed that Ness planned to keep all the loot to herself. If the Survivor tells Ness that she can't keep all the loot, she will tell the mercenaries, who don't know her plan, that the player character planned to take their share of the loot. Then both Ness and the mercenaries will be hostile. Once you kill Ness, there will be a key that belongs to the safe on her corpse. Now the player can take whatever they want or need from the safe.

Opening the safe at the end of the dialogue options will prompt Ness to yell "Thief!", at which point she and the mercenaries become hostile. Of note is that the contents of the safe are green at this point.

Bugs

 * If you miss Ness when she spawns the first time, the quest will end and Ness will be sent to a hidden cell, making this quest unobtainable.
 * It may be possible that Ness will not offer the player character any dialogue when they meet her at the crash site.
 * Solution: console command should move the quest forward.  Note that  will show the quest stages as such: normal is   upon arrival and she cannot talk to the player character,   is after talking with her.
 * If Ness is found close to the Skylanes Flight 1981 crash site and after accepting her offer, going on foot to that place instead of fast-traveling there, the marker that points to where Ness should be to speak with her to start the attack on the raiders will be there, but she will be missing from the place and speaking with the rest of the mercenaries will do nothing to start the attack.
 * A way to fix this (if the crash site was found before meeting Ness) is to reload a save from after meeting her but before going to the crash site, and instead of going on foot using fast-traveling will force Ness to appear where she should be to start the next part of the quest, which is to speak with her to start the attack.
 * Another way is (regardless of when you found the crash site) to teleport the player via console command to the quest target with this command: . Ness will appear and will talk to you and the quest will continue.