QUICK GUIDE: Airline Alliance Benefits [under construction - please help!]
 

In addition to the benefits that one obtains from one's own FF program, the three major airline alliances grant benefits to elites when traveling with partner carriers. Examples include lounge access, special check in and security lines, priority boarding, and additional free checked bags. This thread will serve as a reference for those benefits.

Note that, in addition to alliance partner benefits, many carriers have joint ventures (DL and AF/KLM or AA and BA) or other particularly close relations (UA and LH) with a few partners that result in enhanced benefits. There are also some bilateral partnerships that provide benefits, often with a carrier that doesn't belong to any alliance (for example, Delta and Virgin Atlantic/Virgin Australia) or that may be on the way to joining the alliance.