This achievement can be done by questing, or by trading 148,000 gil to Guddal in Port Jeuno's Kazham Departures area.
*Rise of the Zilart expansion is required for this achievement. It is unobtainable without it.
I obtained this achievement solo as a level 34 WAR/WHM. I had no problem fighting multiple enemies at once, which made the search faster.
The basis of this quest is that you'll need to find three keys. Giddeus Chest Key, Palborough Chest Key, and Ghelsba Chest Key.
My character is from Windurst so did Giddeus first. Travel west through West Sarutabaruta and go to the little inlet in the mountains. Giddeus is located at the southernmost point there, at F-8. You'll want to travel to the middle of Giddeus, and there is a hole you can drop into at H-7. From there, travel South to the very bottom of the map. Don't go too far, or you'll run into a tough Notorious Monster. You're looking for Yagudo Priest, Yagudo Theologist, and Yagudo Votary. These are the three monsters that drop the key. This is the only place you'll find a large number of them, and there is only one Votary you can get to without going the way I instructed. If you're the same level as I was, the monsters should check as Easy Prey. The drop is random, it took me around 20 kills to get the key.
The second key I got was in Ghelsba. I got it while I was completing Windurst Mission 2-3, which is a boss fight in Horlais Peak, inside the area you need to go. To get to the monsters that drop this key, travel to West Ronfaure, and go the northwest portion of the map at E-4. This will put you at Ghelsba Outpost. From there, head directly South to I-11. You'll now be in Yughott Grotto. You need to be looking for Orcish Cursemaker, Orcish Fighter, and Orcish Serjeant. These guys are level 21-23. There are 25 of these monsters total in this area, so if you've killed them all and can't find anymore, make your way to Fort Ghelsba, which is an area joining this one. There's a fresh supply there. This took me around 10 fights to get, and that was on my way to the mission, not specifically questing it.
The last key is the hardest to get, and it also takes the longest to get to. Make it worth your while by picking up the Dark Knight quest before you head all the way out there. Palborough Mines is your destination, which is located located near Bastok at the very top of N. Gustaberg's eastern area, at K-3. Once inside the mines, make your way to the third (top) floor. There are two ways to get up there. The first way is the only way I've ever used, and that's to walk up all of the floors. Almost all of the monsters in the Mines are Too Weak, so it's easy money, and you can get some good synthesis items on the way. I made around 1000 gil by walking up to the top. The second way to get up there is by taking the elevator at I-8. It takes you right up to where you need to be in order to find the three Quadavs you're looking for: Copper, Brass, and Old. These guys are the same level as the other key droppers. This took me around 25 fights to get, but the Quadavs have higher defense then the other monsters, so they take longer. Once you have the key, head to H-8 and take the boat that's there to the Zeruhn Mines. If you have the Dark Knight quest, talk to the NPC to get a sword you'll need, if not, he'll just put you in Zeruhn Mines, which is attached to Bastok Mines.
Now head to Port Jeuno with all of the keys. Trade the keys to an NPC at the Kazham Airship room to get your Kazham Airship Pass.
Don't forget to head to your achievement NPC to unlock it.
Sarute Borute - Windurst Watershttp://wiki.ffxiclopedia.org/wiki/Kazham_Airship_Pass