I'm not a fan of the idea, but I can see some room for Lev-traveling pirates in the setting.
Without boarding actionsFirst of all, we must answer the question:
"Who are Sky Pirates?" They are criminals using Leviathans as tools of violence and robbery. So, they have to now how to pilot and maintain Leviathan. Here we have 3 options:
1) Piloting Leviathan is a piece of cake. Almost everybody can do it;
2) Piloting Leviathan is almost exactly like steering a ship;
3) Special training is required to pilot Leviathan;
Personally, I'm 3rd option's fan. However, option 2 is worth consideration. Lt. Daniel Chandler, gunnery officer of
HML Leviathan, [see: "He who Merits it" - part 1, written by Steven Mohan Jr., published in Lieutenant's Manual] before joining the crew was a sailor on a naval ship. On the other hand, we do not know if he had to be previously trained to command Lev's gunnery fire properly. There is also Lt. Commander Christopher Fermoy, current commander of
HML Hertfordshire and ex-captain of
HMS Vengeance. In this case however, he had a leviathan training on Whale Island [see
HMS Hertfordshire card in Lieutenant's Manual] which can be considered as confirmation of option 3. Oh, and option 1 is just stupid.
So, Sky Pirates are trained Airmen. And they have their own Leviathan.
But how they got one? It's hard to steal a Lev. She rarely lands, and even than she's well guarded in one of military bases. She has numerous crew. I just can't imagine stealing an airship by anybody but her crew.
Summing up, Sky Pirates are airmen who defected and stole their airship.
But what is their goal?They want to be rich. And no, they don't attack other Leviathans. It is not the way to be rich, it's the way to be dead. Leviathans are military machines crewed by soliders. And they usually don't transport anything valuable. The real targets of sky piracy are armless surface ships with valuable cargo. Worktroll described how the attack looks like. IMHO Sky Pirates may also attack isolated settlements to get food supplies etc.
Another question:
How they are able to gain electroid and other hard-to-get stuff needed to operate a Lev?Air pirates also have issues with supplies of ammo, spare parts and electroid. I assume some of you have already considered how to get such things as needed ...
If I'm getting it right, You suggest that Sky Pirates attacks other Levs in order to get electroid, ammo and some precious spare parts. I disagree with you. Attacking warmachine can only results in further damage, electroid leaks, ammo loss plus a few dead pirates. Not worth risking. They may get the stuff in other way. that means Sky Pirates are highly dependent on black marketeers. Probably the most powerful crime organisation involved in illegal goods trading is Italian mafia.
SUMMARYSky Pirates are mostly defected Airmen who have stolen their leviathans. They attack mostly sea transports. They avoid aerial battles. They buy electroid, ammunition and spare parts on the black market.