Most airlines that belong to a global alliance – Star, oneworld, SkyTeam – partner mostly with airlines inside of that alliance. They may have non-alliance partners as well, though those are often limited. For instance American Airlines partners with airlines such as Air Tahiti Nui and Etihad which aren’t part of any alliance.
I like that Korean Air partners with Etihad, as well as Emirates. And they partner with Alaska Airlines and Hawaiian which aren’t alliance members either.
Alaska’s position outside of an alliance means that they’ve built their partnerships out of the backbone of airlines in both SkyTeam and oneworld (and some that are outside of either, like Hainan Airlines and Icelandair).
There’s only a limited number of cases where an airline that is a part of one alliance partners with an airline that’s in another alliance.
You can use United miles to redeem for travel on Aer Lingus (but can no longer use Aer Lingus miles to redeem for travel on United). However Aer Lingus is not yet a member of oneworld, and the United partnership seems highly likely to end once it joins.
Given that, I’m embarrassed to admit that I did not realize Star Alliance member Avianca LifeMiles lets you redeem your miles for travel on Iberia. (Roundtrips are required.)
Redemptions are only available on specific routes, and there’s a separate award chart for Iberia travel — it’s not the same as the Star Alliance award chart. Of course there are no fuel surcharges.
And business class:
These awards are expensive, to be sure. I’d much rather use LifeMiles for travel on Star Alliance airlines. But I had no idea this was possible, even though Iberia is listed as a partner on the LifeMiles site and indeed included on the dropdown box when choosing to search award availability by individual airline online.